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Full-Text Articles in Biochemistry, Biophysics, and Structural Biology

Characterization Of Two Novel Spindle Matrix Proteins In Drosophila, Chromator And Megator , Dong Wang Jan 2003

Characterization Of Two Novel Spindle Matrix Proteins In Drosophila, Chromator And Megator , Dong Wang

Retrospective Theses and Dissertations

A spindle matrix has been proposed to help organize and stabilize microtubules during mitosis. This concept has gained new interest due to the identification of Skeletor as a potential component of the spindle matrix. Skeletor is associated with chromosomes during interphase but reorganizes into a spindle-like structure during early prophase before the nuclear envelope breaks down and microtubules enter the nucleus. The Skeletor spindle extends from pole to pole during metaphase coaligning with the microtubule spindle and persists even after nocodazole treatment dissembles the microtubules. These features make Skeletor an ideal candidate as a spindle matrix protein.;In this study ...


The Mechanism Of Integration Preference To Heterochromatin Of Yeast Retrotransposon Ty5 , Weiwu Xie Jan 2003

The Mechanism Of Integration Preference To Heterochromatin Of Yeast Retrotransposon Ty5 , Weiwu Xie

Retrospective Theses and Dissertations

Ty5 is a retrotransposon in Saccharomyces cerevisiae. In wild type yeast strains, over 90% of Ty5 insertions occur at the telomeres or HM loci. These regions are bound in silent chromatin, which is analogous to heterochromatin of higher eukaryotes. Our laboratory previously described a targeting mutant of Ty5 that has an amino acid substitution near the C-terminus of integrase. Targeting to silent chromatin is reduced more than 20-fold in the mutant. We further defined the Ty5 targeting domain (TD) by saturation mutagenesis. All of the targeting mutations mapped to a stretch of six amino acids (LDSSPP). We tethered TD to ...


Functional Divergence And Genome Evolution Of Vertebrate Protein Kinases (Kinome), Jianying Gu Jan 2003

Functional Divergence And Genome Evolution Of Vertebrate Protein Kinases (Kinome), Jianying Gu

Retrospective Theses and Dissertations

The emerging complete and nearly complete genome sequences have provided a significant amount of materials for large-scale comparative genomic analysis. Novel methods have been developed to elucidate the function of gene products and functional interacting networks. Many of these post-genomic attempts have focused on unveiling the evolutionary forces that have shaped the network organization. Among various evolutionary forces, duplication of functional domain, individual gene, chromosomal segment, or entire genome has long been thought as primary resource for the function novelties in a vast number of gene families. It is therefore intriguing to quantitatively trace the changes of evolutionary constraints after ...


Posttranslational Processing And Functional Analysis Of Tractin, An L1 Family Member In Leech , Yingzhi Xu Jan 2003

Posttranslational Processing And Functional Analysis Of Tractin, An L1 Family Member In Leech , Yingzhi Xu

Retrospective Theses and Dissertations

During neurogenesis, glycosylated cell adhesion molecules (CAMs) mediate the growth cone navigation and synapse formation. The structure of neuronal CAMs of Ig superfamily is characterized by the variability and complexity of their extracellular region which contain multiple tandemly arranged domains. The diversity in the structure of the neuronal CAMs is generated by alternative splicing and posttranslational modification, such as differential glycosylation and proteolytic processing.;Tractin is a member of the L1-family of neuronal CAMs in leech. It contains six Ig domains, 4 FNIII-like domains, an acidic domain, 12 repeats of a novel proline- and glycine-rich motif (PG/YG) with sequence ...


Navigating Heterochromatin , Peter Fuerst Jan 2003

Navigating Heterochromatin , Peter Fuerst

Retrospective Theses and Dissertations

The condensed structure of heterochromatin differs significantly from euchromatin and DNA bound in heterochromatin is generally not transcriptionally active. Transcriptional silencing allows the control of gene expression and affords a novel mechanism of defense against genomic parasites. In addition, the physical structure of heterochromatin plays a direct role by contributing to centromere function in many eukaryotes. Mechanisms by which heterochromatin is established and maintained are only partly understood at this time. By studying the interaction of Ty5, a retrotransposon that integrates preferentially into heterochromatin-bound DNA, some of the basic biology of heterochromatin and the proteins that compose it were elucidated ...


Functional Characterization Of Mitochondrial And Cytosolic Aldehyde Dehydrogenases In Maize (Zea Mays L) , Feng Liu Jan 2002

Functional Characterization Of Mitochondrial And Cytosolic Aldehyde Dehydrogenases In Maize (Zea Mays L) , Feng Liu

Retrospective Theses and Dissertations

Aldehyde dehydrogenases (ALDHs) are a group of enzymes that catalyze oxidation of aldehydes in the presence of coenzyme NAD+ or NADP+. Few plant ALDHs have been studied at protein level, although many ALDH genes have been cloned. To date no functional characterization of plant ALDHs has been reported. This dissertation is focused on functional characterization of four ALDHs from maize, RF2A, RF2B, RF2C and RF2D. RF2A and RF2B are targeted to mitochondria, while RF2C and RF2D are located in cytosol. RF2A is required for normal pollen development: the anthers in lower florets from spikelets of homozygous mutant rf2a plants in ...


Molecular And Genetic Characterization Of Rf2, A Mitochondrial Aldehyde Dehydrogenase Gene Required For Male Fertility In Maize (Zea Mays L) , Xiangqin Cui Jan 2001

Molecular And Genetic Characterization Of Rf2, A Mitochondrial Aldehyde Dehydrogenase Gene Required For Male Fertility In Maize (Zea Mays L) , Xiangqin Cui

Retrospective Theses and Dissertations

T-cytoplasm induced male sterility (cms-T) is a maternally inherited inability to produce viable pollen in maize. The causal factor, the URF13 protein, is encoded by the mitochondrial genome and accumulates in the mitochondrial inner membrane. Fertility restoration of cms-T is mediated by the complementary action of two nuclear genes, rf1 and rf2. The rf2 gene was cloned via transposon tagging. Sequence analysis revealed that it has high sequence similarity to mammalian mitochondrial aldehyde dehydrogenases (mtALDHs). Sequence, mRNA, and protein analyses of the spontaneous mutant allele rf2-R213 demonstrated that the ALDH activity is necessary for rf2's function as a cms-T ...


Coordination Of Cell Morphology And Nuclear Division By The Bud Neck Control Ring In Saccharomyces Cerevisiae , Courtney Lynn Thomas Jan 2001

Coordination Of Cell Morphology And Nuclear Division By The Bud Neck Control Ring In Saccharomyces Cerevisiae , Courtney Lynn Thomas

Retrospective Theses and Dissertations

Coordination of daughter cell growth and nuclear division are readily observed but not well understood in the yeast Saccharomyces cerevisiae . A screen was performed to identify mutants which lost this coordination such that they exhibited an elongated cell morphology (improper cell growth), but continued to divide. The results of this screen and suppressor analysis suggests the bud neck ring is a control structure which determines cell morphology as well as nuclear division as an upstream regulator of Cdc28p-cyclin complexes.;The effects of mutations in specific components of the bud neck ring on the assembly of other components into the structure ...


Studying The Replication Mechanism Of The Yeast Retrotransposon Ty5 By Molecular And Computational Approaches, Xiang Gao Jan 2001

Studying The Replication Mechanism Of The Yeast Retrotransposon Ty5 By Molecular And Computational Approaches, Xiang Gao

Retrospective Theses and Dissertations

The yeast retrotransposon Ty5 is a Ty1/copia element. It is in the Hemivirus genus of the Pseudoviridae family. The ability to genetically manipulate retrotransposons and the yeast host cell was taken advantage of to explore replication mechanisms unique to Ty5 and common to most retrotransposons. Because of the abundance and diversity of retroelement sequences, along with the fact that many retroelement enzymes have evolved unique functional specificities, computational approaches were also developed to study functional divergence in replication. By screening a randomly mutagenized Ty5 library, two mutations (Y68C, D252N) causing higher transposition frequencies were identified. Both mutations increased Ty5 ...


Drosophila Jil-1 Kinase Mediates Histone H3 Ser10 Phosphorylation, Maintains Higher Order Chromatin Structure, And Is Implicated In Dosage Compensation , Yanming Wang Jan 2001

Drosophila Jil-1 Kinase Mediates Histone H3 Ser10 Phosphorylation, Maintains Higher Order Chromatin Structure, And Is Implicated In Dosage Compensation , Yanming Wang

Retrospective Theses and Dissertations

The Drosophila JIL-1 tandem Ser/Thr kinase is associated with chromosomes/chromatin throughout the cell cycle in early embryos and localized to hundreds of sites on the open interband regions on third instar larvae polytene chromosomes. Interestingly, the level of JIL-1 is upregulated on the male X chromosome, which is hypertranscribed for dosage compensation. The distribution of JIL-1 overlaps with that of MSL (male specific lethal) proteins and JIL-1 is associated with the MSL complex.;To further study the function of JIL-1 in vivo, a series of JIL-1 mutants from hypomorphs to null were generated. Analyzing the phenotypes of JIL-1 ...


Characterization Of Skeletor: A Novel Nuclear Protein Implicated In Mitotic Spindle Assembly , Diana Lee Walker Jan 2000

Characterization Of Skeletor: A Novel Nuclear Protein Implicated In Mitotic Spindle Assembly , Diana Lee Walker

Retrospective Theses and Dissertations

The mAb 2A labels Drosophila embryos in a novel, dynamic staining pattern that identifies a nuclear meshwork during interphase, which is remodeled to form a spindle structure at metaphase. This intriguing pattern made the antigens recognized by mAb 2A interesting targets for cloning and analysis, Skeletor was found to be encoded by a complex locus. Two alternatively spliced transcripts from the Skeletor locus were identified, Orf1b/Orf2 and Orf1a. Orf1b/Orf2 has an unusual structure, containing two overlapping open reading frames with coding potentials of 87 kD and 81 kD respectively. Analysis of Orf2 amino acid content reveals overall high ...


Tissue Specific Expression And Regulation Of The Mitogen Regulated Protein Genes , John Tollen Fassett Jan 2000

Tissue Specific Expression And Regulation Of The Mitogen Regulated Protein Genes , John Tollen Fassett

Retrospective Theses and Dissertations

Mitogen Regulated Protein (MRP; also called Proliferin; or MRP/PLF) is a member of the Prolactin/Growth Hormone gene family. There is evidence that MRP/PLF is a uterine growth factor and an angiogenesis factor. Between four and six highly homologous MRP/PLF genes (mrp/plf ) exist in the mouse, but the significance of multiple genes has not been determined. MRP/Plf is produced at high levels during mid-gestation by the placenta, where expression is restricted to the trophoblastic giant cells. To better understand the regulation of the mrp/ plf genes in vivo, we have developed an assay to analyze ...


Molecular And Genetic Analysis Of Jil-1, A Chromatin Associated Protein Kinase Implicated In Transcriptional Regulation In Drosophila , Ye Jin Jan 1999

Molecular And Genetic Analysis Of Jil-1, A Chromatin Associated Protein Kinase Implicated In Transcriptional Regulation In Drosophila , Ye Jin

Retrospective Theses and Dissertations

Chromatin remodeling is an essential step for many chromatin-related fundamental cellular processes, such as gene replication, transcription, recombination and gene silencing. Two classes of protein complexes contribute to chromatin remodeling: protein complexes with ATPase activity and protein complexes capable of enzymatic modifications of chromosomal proteins, especially histones. Compared to well-studied histone acetylation which has been directly linked to gene transcription, the role of histone phosphorylation in chromatin remodeling for gene transcription is still poorly understood although there is some correlation between histone phosphorylation and gene transcription;A novel nuclear tandem protein kinase JIL-1 was cloned and identified in Kristen Johansen ...


Novel G-Dna Binding Proteins From The Ciliate Tetrahymena Thermophila: Purification, Characterization, Cloning And Functional Analyses , Quan Lu Jan 1999

Novel G-Dna Binding Proteins From The Ciliate Tetrahymena Thermophila: Purification, Characterization, Cloning And Functional Analyses , Quan Lu

Retrospective Theses and Dissertations

G-DNA is a family of novel four-stranded DNA structures characterized by motifs called G-quartets. Evidence is growing to suggest that G-DNA exists and plays biological roles in vivo. In order to further elucidate the functions of G-DNA, we have studied proteins that specifically bind to the DNA structure;Two G-DNA binding activities, TGPI and TGP3, were purified from the ciliate Tetrahymena thermophila. Based on the peptide sequences obtained from direct internal peptide sequencing, the cDNAs coding for the genes were cloned. Deduced protein sequences showed that TGP1 and TGP3 are novel proteins but share significant homology with each other. Furthermore ...


Genome Reorganization And Non-Linear Transposition In Maize , Jianbo Zhang Jan 1999

Genome Reorganization And Non-Linear Transposition In Maize , Jianbo Zhang

Retrospective Theses and Dissertations

Transposable elements have long been considered as potential agents of large-scale genome reorganization by virtue of their ability to induce chromosomal rearrangements such as deletions, duplications, inversions, and reciprocal translocations. Previous researchers have shown that particular configurations of transposon termini can induce chromosome rearrangements at high frequencies. By analyzing two derivatives of an unstable allele of the maize P1 (pericarp color) gene carrying both a full-length Ac (Activator) transposable element and a Ac terminal fragment termed fAc (fractured Ac) that were recovered from a classical maize ear twinned sector, it were found that the twinned alleles are a large inverted ...


Molecular Characterization Of Myb-Homologous Transcriptional Factors Of The Flavonoid Pathway In Zea Mays , Peifen Zhang Jan 1999

Molecular Characterization Of Myb-Homologous Transcriptional Factors Of The Flavonoid Pathway In Zea Mays , Peifen Zhang

Retrospective Theses and Dissertations

Structural genes encoding enzymes that catalyze each step of flavonoid synthesis are temporally and spatially regulated. It has been shown that specific anthocyanin pigmentation patterns in maize are achieved by the tissue-specific expression of regulatory genes. Moreover, this tissue-specific regulation is a consequence of the generation of different alleles or duplicated copies of regulatory genes during evolution;In contrast, the myb-homologous P1 gene was the only known regulatory gene required for phlobaphene biosynthesis. The isolation and characterization of the P2 gene, reported here, provides direct molecular evidence that the P region contains duplicated genes. Furthermore, the duplicated P1 (herein, P1-rr ...


Dynamic Changes In The Localization Of Synapse Associated Proteins During Development And Differentiation Of The Mammalian Retina , Mary Heather West Greenlee Jan 1999

Dynamic Changes In The Localization Of Synapse Associated Proteins During Development And Differentiation Of The Mammalian Retina , Mary Heather West Greenlee

Retrospective Theses and Dissertations

We have examined the developmental distribution and differential localization of presynaptic terminal associated proteins in the mammalian retina. We have used antibodies specific for synaptic vesicle associated proteins Synaptotagmin, Rab 3A, Synaptophysin and Synaptobrevin, and presynaptic terminal membrane associated proteins SNAP-25 and Syntaxin, to characterize their spatio-temporal distribution during retinal differentiation and in the mature retina;The vertebrate retina has a laminar organization consisting of three cellular layers separated by two synaptic layers, the inner piexiform layer and the outer plexiform layer. In general, immunoreactivity for presynaptic terminal associated proteins was first observed in cellular layers, and as differentiation progressed ...


Transposon-Induced Homologous Recombination At The Maize P Locus And In Transgenic Arabidopsis , Yongli Xiao Jan 1999

Transposon-Induced Homologous Recombination At The Maize P Locus And In Transgenic Arabidopsis , Yongli Xiao

Retrospective Theses and Dissertations

The maize P gene encodes a Myb-homologous regulator of red phlobaphene pigment biosynthesis in the pericarp, cob and other floral tissues. The P locus has a unique structure with two 5.2kb direct repeats flanking the P gene coding region. When the transposon (Ac) inserts into one site between the two direct repeats in the P-ovov-1114 allele, homologous recombination between the two 5.2kb repeats can occur and the whole P gene coding sequence is deleted;To further study this transposon-induced homologous recombination. This study examined six alleles that carry Ac insertions at different sites in the P locus, in ...


Characterization Of Three Root Hair Mutants In Maize , Tsui-Jung Wen Jan 1998

Characterization Of Three Root Hair Mutants In Maize , Tsui-Jung Wen

Retrospective Theses and Dissertations

Root hairs are thought to play an important role in the uptake of water and nutrients from the environment. Several root hair defective mutants were isolated from Mutator-tagged stocks and EMS-mutagenized lines of maize. These mutants all condition either non-elongated root-hair initials (rth1, rth3-1, rth3-2, rth3-3, rth4, rth5, rth6) or shorter-than-normal root hairs (rth2). The morphology of rth1, rth2, and rth3 root hairs were analyzed via SEM. The rth1, rth2, and rth3 genes map to chromosomes 1L, 5L, and 1S, respectively. The rth3 gene was cloned using Mu-tagged allele. The partial cDNA sequence of this gene suggests that it may ...


Epigenetic Effects Of Matrix Attachment Regions On Transgene Expression In A Maize Callus Line , Cory Ray Brouwer Jan 1998

Epigenetic Effects Of Matrix Attachment Regions On Transgene Expression In A Maize Callus Line , Cory Ray Brouwer

Retrospective Theses and Dissertations

Matrix attachment regions (MARs) are DNA sequences that bind non-histone proteins in the chromatin scaffold and define discrete loops of DNA containing expressed genes in vivo. I have been studying the effects of flanking transgenes with MARs on transgene expression levels in BMS maize callus. Three MAR elements, two from maize (Adhl 5' MAR and Mhal 5' MAR) and one from yeast (ARS1), have very different effects on transgene expression that bear no relation to their affinity for the nuclear matrix in vitro. The main effect of MARs is to prevent silencing of some (but not all) transgenes, at least ...


Host Regulation Of The Replication Of The Yeast Retrotransposon Ty5 , Ning Ke Jan 1997

Host Regulation Of The Replication Of The Yeast Retrotransposon Ty5 , Ning Ke

Retrospective Theses and Dissertations

The replication of retroelements may have deleterious effects on the hosts. Therefore, elements and their hosts have coevolved mechanisms to regulate retroelement replication. This regulation can occur at the transcriptional, translational, or post-translational levels as well as through targeted integration or cDNA recombination. I have studied host regulation of the Saccharomyces retrotransposon Ty5. I have found that Ty5 transcription is carefully controlled. Transcription of Ty5 is haploid specific and is repressed 10 fold in diploid strains. Ty5 transcription is also regulated by the pheromone response pathway, which is activated during mating. In addition, Ty5 transcription is regulated by flanking sequences ...


Regulation Of Brucella Abortus Catalase As A Defensive Mechanism Against Oxidative Stress , Jeonga Kim Jan 1997

Regulation Of Brucella Abortus Catalase As A Defensive Mechanism Against Oxidative Stress , Jeonga Kim

Retrospective Theses and Dissertations

Free radicals in the nature are harmful to organisms because they cause damage to tissues, cell membranes, proteins, and DNA. The animal immune system (cell mediated immune response) uses oxygen molecules to kill foreign organisms. B. abortus causes a cattle disease called brucellosis. The mechanism for bacteria to survive and adapt in the face of oxidative attack is thought to be important for understanding pathogenesis. This dissertation presents the response of B. abortus to oxidative stress and the regulation of catalase as a defensive mechanism;Different protein expression patterns were observed during oxidative stress by conducting 2-D protein gel analysis ...


Differential Glycosylation Of Tractin And Leechcam, Two Novel Ig-Superfamily Members, Regulates Neurite Extension And Fascicle Formation , Yueqiao Huang Jan 1997

Differential Glycosylation Of Tractin And Leechcam, Two Novel Ig-Superfamily Members, Regulates Neurite Extension And Fascicle Formation , Yueqiao Huang

Retrospective Theses and Dissertations

Specific carbohydrate structures on neural cell adhesion molecules are promising candidates for assisting in patterning neural connections during development. An excellent system to study the potential function of specific oligosaccharide modifications of neural proteins regulating pathway formation is in the projections of sensillar neurons in leech. At least five different monoclonal antibodies (Lan3-2, Lan2-3, Lan4-2, Laz2-369, Laz7-79) which recognize different glycoepitopes specific to the entire population as well as distinct subsets of these sensillar neurons have been identified. Their expression patterns and antibody perturbation studies are consistent with the hypothesis that a hierarchy of distinct carbohydrate structures expressed by specific ...


Genetic And Biochemical Analysis Of Aspergillus Awamori Glucoamylase Thermostability , Martin John Allen Jan 1997

Genetic And Biochemical Analysis Of Aspergillus Awamori Glucoamylase Thermostability , Martin John Allen

Retrospective Theses and Dissertations

Aspergillus awamori glucoamylase (GA) is an enzyme involved in industrial corn starch processing. Genetic and biochemical approaches were used to study the mechanisms governing GA thermostability. Three proline substitution (Xaa → Pro) mutations were constructed that were predicted to increase the enzyme's stability by decreasing its conformational entropy of unfolding. When expressed in Saccharomyces cerevisiae Ser30 → Pro increased, Asp345 → Pro did not alter and Glu408 → Pro greatly decreased GA stability as measured by resistance to irreversible thermoinactivation relative to the wild-type enzyme. The Ser30 → Pro mutation was combined with other previously identified stabilizing mutations to examine whether combining such mutations ...


Molecular Cloning And Characterization Of Gl8, A Gene Involved In Maize Cuticular Wax Biosynthesis , Xiaojie Xu Jan 1997

Molecular Cloning And Characterization Of Gl8, A Gene Involved In Maize Cuticular Wax Biosynthesis , Xiaojie Xu

Retrospective Theses and Dissertations

The gl8 locus of maize was previously defined by a mutation that reduces the amount and alters the composition of seedling cuticular waxes. Sixty independently derived gl8 mutant alleles have been isolated from stocks that carried the Mutator transposon system. A DNA fragment that contains a Mu8 transposon and that co-segregates with one of these alleles, gl8-Mu3142, was identified and cloned. DNA flanking the Mu8 transposon was shown to represent the gl8 locus via allelic cross-referencing experiments. The gl8 probe reveals a 1.4-kb transcript present in wild-type seedling leaves, and in lesser amounts, in other organs and at other ...


Cloning And Characterization Of A Soybean Snf2 Yeast Homolog , Weiping Chen Jan 1997

Cloning And Characterization Of A Soybean Snf2 Yeast Homolog , Weiping Chen

Retrospective Theses and Dissertations

It is of great economic and scientific interest to understand plant disease resistance genes at the molecular level. Phytophthora sojae, a fungal pathogen of soybean is of particular interest since the root and stem rot resulting from its infection causes great economic loss. It is the goal of this project to clone Phytophthora resistance genes from soybean. This was done by designing primers from the conserved regions of known plant disease resistance genes using a modified differential display for near isogenic lines; L85-3044 a resistant line and Williams, a susceptible line. Several polymorphic bands were identified, including a unique 0 ...


Studies Of Cis- And Trans-Acting Elements In Tetrahymena Rdna Replication , Chunying Du Jan 1997

Studies Of Cis- And Trans-Acting Elements In Tetrahymena Rdna Replication , Chunying Du

Retrospective Theses and Dissertations

Eukaryotic cells must precisely duplicate their genomes before they divide. The mechanisms of eukaryotic chromosomal DNA replication are far from clear, however, because very few cis- and trans-acting factors that function in eukaryotic DNA replication have been identified. To gain further insights into this problem, this work identified and characterized potential cis- and trans-acting replication factors for the replication initiation of Tetrahymena ribosomal RNA gene (rDNA);A search far cis-acting elements identified a cluster of predicted modular sequences and structural elements in the origin region of rDNA. The presence of these elements were verified experimentally; (1) two mung bean nuclease-hypersensitive ...


Molecular Characterization Of Cer2, An Arabidopsis Gene Involved In Cuticular Wax Accumulation , Yiji Xia Jan 1997

Molecular Characterization Of Cer2, An Arabidopsis Gene Involved In Cuticular Wax Accumulation , Yiji Xia

Retrospective Theses and Dissertations

Cuticular waxes are complex mixtures of very long chain fatty acids (VLCFAs) and their derivatives. The CER2 locus of Arabidopsis is involved in cuticular wax accumulation on stems, siliques, and hypocotyls. The CER2 gene was cloned via chromosome walking. This cloned sequence is able to complement the cer2 mutant phenotype. It is a single-copy sequence in the Arabidopsis genome and encodes a novel protein with a predicted mass of 47 kD. Anti-CER2 polyclonal antibodies detected a 47 kD polypeptide. Cell fractionation and immunoblot analyses demonstrated that the CER2 protein is not membrane-bound and localized in nuclei. These results suggest that ...


Genetic Construction And Biochemical Analysis Of Thermostability Mutants Of Glucoamylase From Aspergillus Awamori , Yuxing Li Jan 1996

Genetic Construction And Biochemical Analysis Of Thermostability Mutants Of Glucoamylase From Aspergillus Awamori , Yuxing Li

Retrospective Theses and Dissertations

To study the molecular basis of Aspergillus awamori glucoamylase (GA) thermostability, eighteen mutants were constructed by site-directed mutagenesis and expressed in Saccharomyces cerevisiae based on thermostability theories. Four lysine residues, K61, K279, K352 and K404, were replaced with arginine, with all but K404 well exposed to the solvent and far away from the enzyme activity site. Mutations K61F/D65E and H254W/E326Q were made to fill a packing void around the inner set of six [alpha]-helices of GA and to displace water molecules inside the void. Five residues (A27, A393, A435, Ser436 and Ser460) were replaced with proline. Two ...


Molecular Characterization Of The Chloroplastic Acetyl-Coa Carboxylase Of Arabidopsis Thaliana , Joong-Kook Choi Jan 1996

Molecular Characterization Of The Chloroplastic Acetyl-Coa Carboxylase Of Arabidopsis Thaliana , Joong-Kook Choi

Retrospective Theses and Dissertations

Acetyl-CoA carboxylase (ACCase) is a biotin-containing enzyme that catalyzes the formation of malonyl-CoA from acetyl-CoA. Dicot plants such as Arabidopsis contain two structurally distinct types of ACCases that are located in different subcellular compartments. The ACCase located in the cytosol of plant cells generates malonyl-CoA for the synthesis of plant secondary metabolites, including a variety of polyketides and derivatives, and malonylated phytochemicals. The ACCase that is located in chloroplasts generates malonyl-CoA for de novo fatty acid biosynthesis. This enzyme has a heteromeric structure consisting of at least four subunits: the biotin-carrier subunit, coded by the CAC1 gene, the biotin carboxylase ...