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

Characterization Of Barley Yellow Dwarf Virus Subgenomic Rnas, Jacquelyn R. Jackson Jan 2008

Characterization Of Barley Yellow Dwarf Virus Subgenomic Rnas, Jacquelyn R. Jackson

Retrospective Theses and Dissertations

Transcription of subgenomic RNAs (sgRNAs) is a common strategy used by many positive strand RNA viruses of plants and animals to regulate viral gene expression. Barley yellow dwarf virus (BYDV) produces three nested 3'-coterminal subgenomic RNAs in infected cells. SgRNA1 serves as the messenger for the structural and movement proteins. sgRNA2 encodes a small open reading frame (ORF6), that appears not to be translated. The role of sgRNA3 is unknown, as it encodes no ORFs. Neither sgRNA2 nor sgRNA3 is needed for BYDV RNA replication in oat protoplasts. However, sgRNA2 does function as a riboregulator of viral translation in ...


Biotechnological Improvements Of Bio-Based Fuels And Lubricants: Characterization Of Genes For Branched Chain Fatty Acids And Mono-Acyl Esters, Yuqin Jin Jan 2007

Biotechnological Improvements Of Bio-Based Fuels And Lubricants: Characterization Of Genes For Branched Chain Fatty Acids And Mono-Acyl Esters, Yuqin Jin

Retrospective Theses and Dissertations

The goals of the research in this dissertation are to generate the fundamental technologies that can be used to improve the production and quality of vegetable-oil based biodiesel and biolubricants. Specifically, we sought to test the hypothesis that branched chain fatty acids (BCFAs) can substitute for unsaturated fatty acids in maintaining fluidityin an organism. Toward this goal, we examined the utility of two Bacillus keto-acyl synthase III (KASIII) coding genes (yhfB and yjaX) in producing BCFAs. In conducting this research it was necessary to examine if the E. coli KASIII gene (fabH) was essential for initiating fatty acid biosynthesis and ...


Molecular Basis Of Campylobacter Antibiotic Resistance And Adaptation To The Intestinal Tract Of Chickens, Baoqing Guo Jan 2007

Molecular Basis Of Campylobacter Antibiotic Resistance And Adaptation To The Intestinal Tract Of Chickens, Baoqing Guo

Retrospective Theses and Dissertations

Campylobacter is a major foodborne pathogen causing human enteric infections. Antibiotic treatments are needed for prolonged and severe cases of campylobacteriosis, but Campylobacter is increasingly resistant to antimicrobials, which has rendered antimicrobial therapy less effective. Multiple mechanisms contribute to antibiotic resistance in Campylobacter, but antibiotic efflux mediated by membrane transporters is considered a significant player in conferring intrinsic and acquired resistance to a broad spectrum of antimicrobials. The recently published genomic sequence revealed the presence of multiple genes encoding efflux transporters in C. jejuni, and work conducted in our laboratory identified that CmeABC, a RND (resistance nodulation and cell division ...


Methanobactin And The Membrane-Associated Methane Monooxygenase In Methanotrophy: A Tale Of Two Proteins, Dongwon Choi Jan 2007

Methanobactin And The Membrane-Associated Methane Monooxygenase In Methanotrophy: A Tale Of Two Proteins, Dongwon Choi

Retrospective Theses and Dissertations

No abstract provided.


Genetic Profiling Of Mycoplasma Hyopneumoniae , Melissa L. Madsen Jan 2005

Genetic Profiling Of Mycoplasma Hyopneumoniae , Melissa L. Madsen

Retrospective Theses and Dissertations

A microarray was constructed and applied to transcriptional profiling and genetic variation studies of Mycoplasma hyopneumoniae. The genome sequence enabled the construction of the microarray to allow a global approach to understanding fundamental processes in M. hyopneumoniae . These studies focused on whether M. hyopneumoniae regulates its genes under different environmental conditions and if genetic changes can be correlated with virulence. The microarray consisted of 632 open reading frames represented by polymerase chain reaction products and were used in a two-color experimental design. Data were analyzed using a mixed linear statistical model. Unique features implemented in these studies included the printing ...


Cell Envelope Constituents Of Pseudomonas Putida Contributing To Growth And Survival In Low-Water-Content Habitats , Martinus Franciscus Maria Van De Mortel Jan 2005

Cell Envelope Constituents Of Pseudomonas Putida Contributing To Growth And Survival In Low-Water-Content Habitats , Martinus Franciscus Maria Van De Mortel

Retrospective Theses and Dissertations

The ability of bacteria to respond to the ever changing environmental conditions they encounter requires the utilization of a broad range of colonization and survival strategies. One of the most important and probably least understood factors determining bacterial activity in terrestrial habitats is water availability. The goal of this dissertation research was to identify traits that contribute to maintaining a functional cell envelope when cells are dehydrated, which will help us to assess the scope of physiological changes necessary for growth in low-water-content habitats. The primary objective was to identify genes that are specifically regulated by dehydration (matric stress), and ...


Subunits Of Highly Fluorescent Protein R-Phycoerythrin As Probes For Cell Imaging And Single-Molecule Detection , Dragan Isailovic Jan 2005

Subunits Of Highly Fluorescent Protein R-Phycoerythrin As Probes For Cell Imaging And Single-Molecule Detection , Dragan Isailovic

Retrospective Theses and Dissertations

R-phycoerythrin (R-PE) subunits and enzymatic digests were characterized by high-performance liquid chromatography (HPLC), capillary and gel electrophoresis, and HPLC-electrospray ionization mass spectrometry. Subunits were isolated from R-PE by HPLC and detected as single molecules by total internal reflection fluorescence microscopy (TIRFM). Favorable spectroscopic characteristics of R-PE subunits and digest peptides in the visible region of spectrum originate from phycoerythrobilin (PEB) and phycourobilin (PUB) chromophores. High absorption coefficients and fluorescence (even under denaturing conditions), broad excitation and emission fluorescence spectra, and low molecular weights make these molecules suitable for fluorescence labeling of biomolecules and cells.;Fluorescent proteins were further formed both ...


Investigation Of Microcin 24 For Applications In Food Safety, Mechanism Of Resistance And Effect On Activity After Site-Directed Mutagenesis , Timothy Steven Frana Jan 2004

Investigation Of Microcin 24 For Applications In Food Safety, Mechanism Of Resistance And Effect On Activity After Site-Directed Mutagenesis , Timothy Steven Frana

Retrospective Theses and Dissertations

Microcin 24 is an antimicrobial peptide produced by Escherichia coli with activity against Salmonella typhimurium. In this study microcin 24 was investigated for its potential use in food safety, resistance development, and structure-activity relationship following site-directed mutagenesis. An attempt was made to produce microcin 24 from lactic acid bacteria by substituting the natural, dedicated leader peptide microcin-producing gene with a signal leader from divergicin A, which accesses the general secretion pathway. RNA sequences could be recovered from Carnobacterium divergens harboring an expression vector with the fusion construct, but no microcin activity could be detected. Concurrently, development and mechanism of resistance ...


Gene Regulation Of Rna Viruses With Uncapped And Non-Polyadenylated Genomic Rna , Ruizhong Shen Jan 2004

Gene Regulation Of Rna Viruses With Uncapped And Non-Polyadenylated Genomic Rna , Ruizhong Shen

Retrospective Theses and Dissertations

New roles of RNAs as regulators of gene expression have emerged and expanded in recent years. However, gene regulation by viral RNA in trans is less noted and not well understood. Barley yellow dwarf virus (BYDV) is a positive sense RNA virus with a single genomic RNA (gRNA). As it replicates it generates three subgenomic RNAs (sgRNA). Data in this dissertation show that BYDV sgRNA2 serves as a regulatory RNA to control viral gene expression. In vitro and In vivo, BYDV sgRNA2 inhibits translation of gRNA, but has less or little effect on translation of sgRNA1, respectively. These data support ...


The Role Of Rev-Sr Protein Interactions In The Regulation Of Equine Infectious Anemia Virus Replication , Gregory Saang Park Jan 2003

The Role Of Rev-Sr Protein Interactions In The Regulation Of Equine Infectious Anemia Virus Replication , Gregory Saang Park

Retrospective Theses and Dissertations

Equine infectious anemia virus (EIAV) is a member of the lentivirus subfamily of retroviruses that produces a variable clinical disease course characterized as acute, chronic, and inapparent. The clinical signs can vary according to the stage of disease, and generally correlate with levels of virus replication. As with other retroviruses, EIAV utilizes both RNA and proteins to produce alternatively spliced transcripts required for virus replication. EIAV encodes a protein called Rev, which functions by binding unspliced and singly spliced viral mRNAs in the nucleus at a sequence called the Rev responsive element (RRE) and exporting them into the cytoplasm. Rev ...


Genetic And Phenotypic Variation Of The Equine Infectious Anemia Virus Surface Unit Envelope Glycoprotein During Disease Progression , Brett Alan Sponseller Jan 2003

Genetic And Phenotypic Variation Of The Equine Infectious Anemia Virus Surface Unit Envelope Glycoprotein During Disease Progression , Brett Alan Sponseller

Retrospective Theses and Dissertations

Lentiviruses are single-stranded RNA viruses generally associated with chronic diseases of the immune and central nervous systems. In contrast to the insidious, progressive nature of most lentiviral diseases, equine infectious anemia virus (EIAV) infection results in rapid onset of a variable disease course in equids. Acute disease is accompanied with high-titered viremia, thrombocytopenia, fever, depression, and inappetance. The chronic stage is usually characterized by recurrent episodes of disease. Equids that survive recurrent disease episodes progress to the inapparent stage of disease where no clinical signs are evident; however, there is persistent, ongoing virus replication. Lentiviruses exist within the host as ...


Characterization Of The Ftsyex Operon Of Escherichia Coli , Becky Graham Jan 2002

Characterization Of The Ftsyex Operon Of Escherichia Coli , Becky Graham

Retrospective Theses and Dissertations

The ftsYEX operon of Escherichia coli historically has been described as a cluster of essential cell division genes. Filamentation temperature-sensitive (fts) designates a class of mutants that displays normal cell morphology at the permissive temperature of 30°C, but filaments and dies at the restrictive temperature of 42°C. The first gene, ftsY, is known to encode an essential component of a protein localization system first described in eukaryotes, the signal recognition particle (SRP) pathway. The function of the following genes, ftsE and ftsX, are much less understood. It has been shown that FtsE and FtsX comprise a two-component ATP-binding ...


Molecular Mechanisms Of Cap And Poly(A) Independent Translation Of Barley Yellow Dwarf Virus Rna , Edwards M. Allen Jan 2001

Molecular Mechanisms Of Cap And Poly(A) Independent Translation Of Barley Yellow Dwarf Virus Rna , Edwards M. Allen

Retrospective Theses and Dissertations

Barley yellow dwarf virus RNA contains a translation element (3 'TE) that confers efficient cap-independent initiation at the 5 proximal AUG. Direct end-labeling of RNAs verified the absence of a 5 ' modification on virion RNA. Thus BYDV differs from related viruses by having neither a genome-linked protein nor a 5 ' cap. To function in the 3' UTR, the 3 'TE must recruit ribosomes and associated translation factors, and communicate with the 5' end of the mRNA where translation initiates. The communication function is mediated by direct base pairing between the 3'TE and the 5' UTR. We propose that protein ...


Phospholipase C Of Clostridium Hemolyticum: Gene Characterization And Proof Of Its Role As A Protective Immunogen In Guinea Pigs , Paul Joseph Hauer Jan 2001

Phospholipase C Of Clostridium Hemolyticum: Gene Characterization And Proof Of Its Role As A Protective Immunogen In Guinea Pigs , Paul Joseph Hauer

Retrospective Theses and Dissertations

The phospholipase C (PLPC) gene from Clostridium hemolyticum was cloned using the polymerase chain reaction. An open reading frame which encodes a 399-amino acid protein, containing a 27-amino acid signal sequence, was identified. The molecular weight of the active protein was 42,869 daltons. A 16-amino acid N-terminal sequence determined by Edman degradation exactly matched the putative amino acid sequence of the gene product. Comparison of the nucleotide and amino acid sequences with Genebank databases demonstrated that the beta toxin of C. hemolyticum exhibits high homology with other bacterial PLPCs. The N-terminal portion of the beta toxin contains the zinc-binding ...


Bacteriophage Therapy: A Novel Method Of Lytic Phage Delivery , Ratree Platt Jan 2000

Bacteriophage Therapy: A Novel Method Of Lytic Phage Delivery , Ratree Platt

Retrospective Theses and Dissertations

The widespread emergence of multi-antibiotic resistant bacteria has increased the need for alternatives to conventional antibiotic therapy. Accordingly, a significant amount of effort has been made to investigate the potential use of bacteriophages as prophylactic and therapeutic agents for bacterial infections. In this study, molecular biological techniques were applied to construct a lysogen of lytic bacteriophage lambda in an attempt to combat with multi-antibiotic resistant bacteria by a novel method of lytic phage delivery;To accomplish this goal, two plasmid-based site-specific recombination (SSR) systems for integration and recovery of DNA constructs from Escherichia coli and Salmonella typhimurium chromosomes were developed ...


Genetic And Molecular Characterization Of The Rev Protein Of Equine Infectious Anemia Virus , Michael Andrew Belshan Jan 1999

Genetic And Molecular Characterization Of The Rev Protein Of Equine Infectious Anemia Virus , Michael Andrew Belshan

Retrospective Theses and Dissertations

Members of the lentivirus subfamily of retroviruses are characterized as causing slow, chronic disease. Atypical of other lentiviruses, such as human immunodeficiency virus type 1, equine infectious anemia virus (EIAV) may produce a rapid, variable disease course in horses. Infected horses may undergo an, acute episode of disease involving viremia, fever, and thrombocytopenia. Following this acute period, horses may resolve to an inapparent infection or suffer a chronic period of additional cycles of viremia, fever, and thrombocytopenia. Horses which survive clinical episodes usually become inapparent carriers of the virus for life. Numerous virus and host factors contribute to the phenotypic ...


Genetic Mobility And Instability Of Retroviral Vector In Vector Producer Cells For Gene Therapy, Won-Bin Young Jan 1999

Genetic Mobility And Instability Of Retroviral Vector In Vector Producer Cells For Gene Therapy, Won-Bin Young

Retrospective Theses and Dissertations

A primary biosafety issue of retroviral vector-mediated gene therapy is the genetic instability of retroviral vectors. Reverse transcription of vector RNA genome is initiated by viral reverse transcriptase (RT) in a virion particle after infection of a target cell. During reverse transcription, abnormal template switches between vector and occasionally co-packaged helper virus in a virion particle can therefore enable helper virus to regain replication elements from the vector and revert to replication-competent retrovirus (RCR). This research was undertaken to study the origins of RT enzyme activities and test the hypothesis that RT enzyme activities are contributed by both exogenous RT ...


Evaluation Of Mycobacterial Esat-6 As A Type-I Immune Enhancing Adjuvant , Sreekumar Ambalakkat Menon Jan 1999

Evaluation Of Mycobacterial Esat-6 As A Type-I Immune Enhancing Adjuvant , Sreekumar Ambalakkat Menon

Retrospective Theses and Dissertations

The need for improved adjuvants has continued in spite of new vaccination strategies using recombinant proteins and genetic (DNA vectored) vaccines. The Mycobacterium tuberculosis protein ESAT-6 has been shown in mice to be involved in the recall of long-lived immunity and protection in mice against tuberculosis. Thus, this protein could potentially act as a molecular adjuvant enhancing antigen-specific Type I immune responses. This study examined the hypothesis that Es could enhance Type I responses against a second antigen in mice when presented as a fusion with that antigen. This was tested using ESAT-6 fusions with two Mycoplasma hyopneumoniae surface antigens ...


X-Ray Crystallographic Studies On Adenylosuccinate Synthetase From Escherichia Coli , Zhenglin Hou Jan 1998

X-Ray Crystallographic Studies On Adenylosuccinate Synthetase From Escherichia Coli , Zhenglin Hou

Retrospective Theses and Dissertations

Adenylosuccinate synthetase catalyzes the first committed step in de novo biosyntheses of AMP from IMP and aspartate, using GTP as the energy source. Metal cations, ligand-induced conformational transitions and metabolic effectors significantly influence the catalytic potential of the synthetase. The Mg2+, Mn2+, or Ca 2+ bind to the same site, coordinating alpha-, beta-, and gamma-phosphoryl groups of GTP. The level of catalysis supported by each cation is linked to its influence on the basicity of Asp13, a residue which abstracts the proton from N1 of IMP. Zn2+, a potent inhibitor of the synthetase, coordinates the beta- and gamma-phosphoryl groups of ...


Analysis Of Viral Proteins Of Porcine Reproductive And Respiratory Syndrome Virus In Host Protection And Early Virus-Cell Interactions , Yanjin Zhang Jan 1998

Analysis Of Viral Proteins Of Porcine Reproductive And Respiratory Syndrome Virus In Host Protection And Early Virus-Cell Interactions , Yanjin Zhang

Retrospective Theses and Dissertations

The viral proteins of porcine reproductive and respiratory syndrome virus (PRRSV) were expressed in a baculovirus expression system. They were evaluated for protection of pigs against the respiratory disease and for function in virus-cell interactions. The open reading frames 2 to 6 products were confirmed to be membrane associated proteins as they were detected on the surface of viable insect cells by an immunofluorescence assay. Immunization of pigs with vaccines comprised of a combination of GP2, GP3 and GP4 or a combination of GP5, M and N proteins induced partial protection, but immunization with combination of GP5 and M proteins ...


Hole Burning With Pressure And Electric Field: A Window On The Electronic Structure And Energy Transfer Dynamics Of Bacterial Antenna Complexes , Hsing-Mei Wu Jan 1998

Hole Burning With Pressure And Electric Field: A Window On The Electronic Structure And Energy Transfer Dynamics Of Bacterial Antenna Complexes , Hsing-Mei Wu

Retrospective Theses and Dissertations

Light-harvesting complexes of cyclic symmetry from purple bacteria are studied using absorption and high pressure- and Stark-hole burning spectroscopies. The B800→B850 energy transfer rate of (~2 ps)-1 determined by hole burning and pump-probe spectroscopies is weakly dependent on B800-B850 energy gap varied by pressure and temperature. This resilience is explained in terms of a modified Forster theory with the spectral overlap provided by the B800 fluorescence origin band and weak vibronic absorption of B850. Explanations for the additional sub-picosecond relaxation channel of B800 with excitation on the blue side are given. Pressure and temperature dependent studies show that ...


Monitoring Protein Refolding Using Diverse Separation And Spectroscopy Techniques , Pamela Kay Jensen Jan 1997

Monitoring Protein Refolding Using Diverse Separation And Spectroscopy Techniques , Pamela Kay Jensen

Retrospective Theses and Dissertations

Rapid growth in the biotechnology industry has led to a dramatic increase in attention to the protein folding problem. Understanding of protein folding is essential to the production of biopharmaceuticals since commercial production of recombinant proteins often requires a protein refolding process to recover high yields;Capillary zone electrophoresis (CZE) equipped with laser induced fluorescence detection (LIFD) is developed as a tool for monitoring the refolding of a model protein, phage P22 tailspike endorhamnosidase. Intermediates on the folding pathway are separated in CZE and monitored by their intrinsic tryptophan fluorescence. Monitoring refolding of tailspike by traditional methods, sodium dodecyl sulfate-polyacrylamide ...


Identification Of Genes In Tn916 Encoding Membrane-Targeted Proteins, Suganda Loe Jan 1997

Identification Of Genes In Tn916 Encoding Membrane-Targeted Proteins, Suganda Loe

Retrospective Theses and Dissertations

Tn916 is a 18 kb, broad-host range conjugative transposon originally isolated from Enterococcus faecalis. Transposon TnphoA was used to identify genes in Tn916 encoding for membrane-targeted proteins or for secretion. Sixty five independent PhoA+ gene fusions were isolated. These insertions clustered into two regions, open reading frames 13 and 15 (Flanagan et al., Plasmid 32:350-354). These TnphoA insertional mutations in resulted in a Tn+ (ability to transpose intracellularly) and Tra- (inability to transfer conjugatively) phenotype. The hydrophathy analysis of ORF13 and ORF15 revealed that these proteins lack the classical signal peptides necessary for protein export, suggesting that these two ...


Sequence And Functional Analysis Of The P97 Swine Cilium Adhesin Gene Of Mycoplasma Hyopneumoniae , Tsungda Hsu Jan 1997

Sequence And Functional Analysis Of The P97 Swine Cilium Adhesin Gene Of Mycoplasma Hyopneumoniae , Tsungda Hsu

Retrospective Theses and Dissertations

Mycoplasma hyopneumoniae causes swine enzootic pneumonia, an important disease in the swine industry. Adherence of M. hyopneumoniae to the cilia of the tracheal epithelial cells is required to establish infection. Previous studies have identified a 97-kDa protein (P97) as the putative ciliary adhesin. To further characterize the P97 protein, the gene has been cloned, its DNA sequence analyzed, and the function of the P97 protein expressed in Escherichia coli studied. These results demonstrated that recombinant P97 has swine ciliary adherence activity. Further analysis revealed that the P97 gene was translated as a 124.9-kilodalton (kDa) protein and subjected to proteolytic ...


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 ...


Replication Of Barley Yellow Dwarf Luteovirus-Pav Rna , Mohan Bangalore Jan 1997

Replication Of Barley Yellow Dwarf Luteovirus-Pav Rna , Mohan Bangalore

Retrospective Theses and Dissertations

Barley yellow dwarf luteovirus (BYDV)-PAV serotype, an economically important virus of small grain cereals, has a positive-sense RNA genome encoding at least six open reading frames (ORFs). The goal of the research was to determine the genes and sequences involved in the viral replication and to design efficient antiviral strategies to BYDV-PAV. Genetically engineered resistance is essential for BYDV as the natural resistance is inadequate. Antiviral constructs such as sense RNA, antisense RNA and viral polymerase gene were tested for their ability to reduce virus titre in oat protoplasts as monitored by enzyme-linked immunosorbent assay. All antiviral constructs yielded ...


The Role Of Domain E In The Activity Of Bacillus Macerans Cyclodextrin Glucanotransferase , Hai-Yin Chang Jan 1997

The Role Of Domain E In The Activity Of Bacillus Macerans Cyclodextrin Glucanotransferase , Hai-Yin Chang

Retrospective Theses and Dissertations

Cyclodextrin glucanotransferase (CGT) folds into five domains A, B, C, D and E. Domain E has the ability to bind starch and cyclodextrins (CDs) and is considered the starch-binding domain of CGT. The role of domain E in the catalysis of Bacillus macerans cyclodextrin glucanotransferase was investigated by constructing five CGT mutants. The truncated CGT (CGT[delta]E) mutant was constructed by deleting domain E, and the chimeric CGT (CGT-SBD) by replacing domain E with the starch-binding domain (SBD) of Aspergillus glucoamylase I. The modified CGT (CGT+6) was constructed by inserting a six-amino-acid pseudo linker between domains D and ...


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 ...


Integration Specificity Of The Retrovirus-Like Transposable Element Ty5 Of Saccharomyces , Sige Zou Jan 1996

Integration Specificity Of The Retrovirus-Like Transposable Element Ty5 Of Saccharomyces , Sige Zou

Retrospective Theses and Dissertations

The retrotransposons and retroviruses display a strong preference in selecting integration sites. The molecular mechanisms underlying this process, however, are largely unknown. I have characterized a new retrotransposon, called Ty5, in diverse strains of Saccharomyces cerevisiae and related species. A functional element, Ty5-6p, was identified from S. paradoxus. To investigate Ty5 target preference, the locations of 13 native insertions were determined in S. cerevisiae and S. paradoxus. Twelve were found near the telomeres and the mating locus HMR. To determine if this distribution is a consequence of targeted integration, a Ty5 transposition assay was developed in S. cerevisiae using Ty5-6p ...