Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Document formatted into pages; contains xi, 98 p.; also includes graphics. Includes bibliographical references (p. 93-98). Available online via OhioLINK's ETD Center

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The Saccharomyces cerevisiae SKN7 gene has been identified through a search for genes which, at a high copy number, could restore the growth of the $kre9 Delta$ disrupted strain showing a cell wall $ beta$-glucan defect. SKN7 was mapped to the right arm of chromosome VIII, and is predicted to encode a 70 kDa protein, Skn7p, with a region of homology to the DNA binding domain of the yeast heat shock transcription factor, Hsf1p. Skn7p also has a domain which shows similarity to the prokaryotic receiver modules found on an extensive family of two-component response regulators, including the product of the rcsC gene. While restoring the growth rate to near wild type levels, SKN7 does not appear to restore the $ beta$-glucan levels of the $kre9 Delta$ mutant. However, SKN7-suppressed cells show a partially restored cellular morphology, and a restored cell wall resistance to mechanical stress. SKN7 does not suppress other mutations in the ($1 rightarrow6$)-$ beta$-glucan biosynthetic pathway, suggesting that it does not act as a general bypass suppressor of this glucan.

The Saccharomyces cerevisiae KEX1 gene product, Kex1p, has been identified and partially characterised to assess its role in processing secreted protein precursors and to define its intracellular location. Kex1p antiserum identified a 113 kDa protein that was absent in kex1-$ Delta$ cells and more abundant in cells overexpressing KEX1. Kex1p was found to be a type I membrane associated glycoprotein with N-linked carbohydrate. The N-linked oligosaccharide was modified in a progressive manner after synthesis, causing the glycoprotein to slowly increase in mass to 115 kDa. / After a Kex2p-mediated cleavage event at specific pairs of basic amino acids, $ alpha$-factor and K1 killer toxin precursors have COOH-terminal dibasic residue extensions and require a carboxypeptidase B-like activity to process the precursors to maturity. A carboxypeptidase activity, with apparent specificity for basic amino acids, was detected in KEX1 cells. Disruption of the KEX1 gene abolished this activity, while overexpression of KEX1 increased it. These results provide biochemical evidence, consistent with earlier genetic work, that KEX1 encodes a serine carboxypeptidase involved in the processing of precursors to secreted mature proteins. / Immunological and activity studies indicate that most Kex1p is intracellular and suggests that the enzyme is retained within the secretory pathway. COOH-terminal truncations of the protein indicate that the cytoplasmically exposed domain of Kex1p is responsible for correct localisation of the protein, probably in the late Golgi. / When KEX1 was expressed in Schizosaccharomyces pombe, Kex1p was localised in structures consistent with components of the Golgi. Mammalian cells expressing KEX1 produce a membrane associated activity that is not detected in the medium. In immunofluorescence studies on mammalian cells, Kex1p was localised to the ER and Golgi but not to the plasma membrane. Kex1p in such cells was responsible for completing the processing of the neuropeptide, $ gamma$-lipotropin. This in vivo processing of $ gamma$-lipotropin by Kex1p demonstrates a significant functional homology of the basic prohormone processing machinery in yeast and neuroendocrine cells.

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Thesis (Ph. D.)--Ohio State University, 2003. / Title from first page of PDF file. Document formatted into pages; contains xxii, 172 p. : ill., some col. Includes abstract and vita. Advisor: Michael K. Chan, Dept. of Chemistry. Includes bibliographical references (p. 165-172).

Carboxypeptidase Y (E.C. 3.4.12.1) was produced from Kluyveromyces fragilis ATCC 28244. The maximum growth and enzyme production were obtained during 24 hr of growth at the late logarithmic phase with optimized conditions (25$ sp circ $C, 300 rpm, pH 5) using YPD (1% yeast extract, 2% peptone, 2% dextrose, w/v) broth medium. A Fast Protein Liquid Chromatography (FPLC) was used for the enzyme purification. The enzyme was purified to 216 fold over the crude extract with a recovery of 18%. The apparent molecular weight of the purified enzyme was estimated to be 120 kDa on Native-PAGE and 56 kDa on SDS-PAGE suggesting that carboxypeptidase Y from Kluyveromyces fragilis consists of two subunits. The pH and temperature optima of the enzyme were pH 6.0 and 35$ sp circ$C, respectively. The enzyme activity was strongly inhibited by diisopropylphosphofluoridate (DIPF) and phenylmethylsulfonylfluoride (PMSF), and caused an average 50% loss of activity when incubated with various metal cations. / The apparent K$ sb{ rm m}$ and V$ sb{ rm max}$ values obtained for n-benzoyl-L-tyrosine-p-nitroanilide (BTPNA) and carboxybenzoxyphenylalanylalanine (Cbz-Phe-Ala) were 5.1 mM and 13.4 $ mu$mole/min/mg and 2.98 mM and 22.58 $ mu$mole/min/mg, respectively. Carboxypeptidase Y hydrolysis on the tryptic digests of $ alpha sb{ rm s1}$- and $ beta$-casein showed that the enzyme randomly removed five and three hydrophobic peptides, respectively and greatly reduced the size and heights of the other peptides analysed on Reversed Phase-High Performance Liquid Chromatography (RP-HPLC).

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Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 159-176).