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Elucidation Of The Players And Events Regulating The First Meiotic Division In Mouse Spermatocytes, Amy Lynn Inselman

Doctoral Dissertations

Meiosis is the process that ensures the continued propagation of new organisms and is a source of genetic variability within a population. During meiotic prophase many dynamic rearrangements occur in the nucleus of the cell. These rearrangements include homologous chromosome pairing, recombination, synaptonemal complex breakdown, chromosome condensation and spindle assembly. The regulatory mechanisms behind these complex processes at the G2/MI transition have not been completely elucidated, preventing our complete understanding of the processes. The purpose of this work is to provide new insight to the events and players involved in the regulation of the G2/MI transition in mouse spermatocytes.

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Role Of Ionic Interactions In The Catalytic Mechanism Of R67 Dihydrofolate Reductase, Stephanie Nicole Hicks

Masters Theses

The goal of this research is to investigate the role of K32 and K33 in the catalytic mechanism of R67 dihydrofolate reductase (DHFR). K32 is located in the active site pore and is the only charged residue in the active site while K33 is located on the surface of R67 DHFR. Both of the ligands for R67 DHFR, NADPH and dihydrofolate (DHF), have negative charges capable of forming ionic interactions with symmetry related K32 residues. NMR, DELPHI, and docking studies predict that K32 is involved in ionic interactions with the 2’phosphate of NADPH. Docking studies also predict that K32 participates …

Involvement Of Transit Peptide Aromatic Residues In Precursor Interaction(S) With The Chloroplast Import Apparatus, Huixia Zhang

Masters Theses

The import of nuclear-encoded preproteins into chloroplast is mediated by the transit peptide located in the N-terminus of the preproteins. A semi-conserved FGLK motif is identified in most of the transit peptides bioinformatically, despite the lack of homology in the primary sequence. To investigate the role of phenylalanines in the FGLK motifs of SStp in the interaction with outer envelope import apparatus, mutations were made on the two motifs found in prSSU from tobacco: F26TGLK and F35PVSRK. These mutations include F→W, F→S, and F→A in both of the motifs. The WT precursor (prSSU), 6 single prSSU mutants, 9 double prSSU …

Identifying The Catalytic And Ligand Binding Roles Of Active Site Residues In Homotetrameric R67 Dihydrofolate Reductase, Michael Brad Strader

Doctoral Dissertations

R67 dihydrofolate reductase (DHFR) is a novel protein that confers clinical resistance to trimethoprim (TMP). Surprisingly, this R-plasmid encoded enzyme does not share homology with chromosomal DHFR. Recently a high resolution crystal structure of R67 DHFR has been solved. From this structure, R67 DHFR is a homotetramer that possesses exact 222 symmetry and a single active site pore that traverses the length of the protein (Narayana et al., 1995). Although this symmetry implies that four symmetry related binding sites must exist for each substrate, isothermal titration calorimetry studies indicate only two molecules bind. Three possible combinations of bound ligands have …