There is a long-standing interest to characterize the molecular events that mediate the production and processing of ergosterol biosynthesis as a strategy for selective chemical targeting of antifungals for therapeutics discovery and development. The focus of this proposal will be on ergosterol synthesis and the family of sterol methyl transferase (SMT) enzymes from Candida albicans, Cryptococcus neoformans, Histoplasma capsulatum and Pneumocystis carinii. Four projects are outlined: 1) Establish the de novo pathway to ergosterol in the test fungi using 13C-labeled intermediates. 2) Evaluate the growth, sterol composition and SMT activity of the test fungi treated with a set of drugs synthesized in our laboratory to serve as single-action (inhibit SMT activity) or dual-action (inhibit SMT and 14a-demethylase activities) inhibitors of ergosterol synthesis. The kinetics of SMT activity in response to substrate analogs will be explored as a means to fashion novel inhibitors. 3) The sterol composition of P. carinii is plant-like in having 24-methyl and 24-ethyl sterols and these """"""""phytosterols"""""""" are regarded as signature lipids for diagnostic purposes. We recently cloned the P. carinii SMT by a PCR-based homology strategy from ESTs provided by a cooperator. We will determine whether the properties of the P. carinfi SMT are similar to the properties of the C. albicans SMT. Purification of the C. albicans and P. carinii SMTs will be achieved after subcloning the relevant cDNA into a Escherichia coil expression system. Chemical affinity and photoaffinity labeling will be used to identify the sterol and AdoMet-binding subdomains, respectively, in the active center. Site-directed mutagenesis followed by activity assay will be employed to probe the functional importance of select residues involved with catalysis. 4) The three-dimensional structure of a SMT will be defined with the aid of a cooperator. The results from these studies will facilitate the design of therapeutic strategies aimed to provide species-specific discrimination of inhibition in the ergosterol biosynthetic pathway.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM063477-03
Application #
6636683
Study Section
AIDS and Related Research 8 (AARR)
Program Officer
Jones, Warren
Project Start
2001-05-01
Project End
2005-04-30
Budget Start
2003-05-01
Budget End
2004-04-30
Support Year
3
Fiscal Year
2003
Total Cost
$181,770
Indirect Cost
Name
Texas Tech University
Department
Chemistry
Type
Schools of Arts and Sciences
DUNS #
041367053
City
Lubbock
State
TX
Country
United States
Zip Code
79409
Nes, W David (2011) Biosynthesis of cholesterol and other sterols. Chem Rev 111:6423-51
Lepesheva, Galina I; Hargrove, Tatyana Y; Kleshchenko, Yuliya et al. (2008) CYP51: A major drug target in the cytochrome P450 superfamily. Lipids 43:1117-25
Song, Zhihong; Nes, W David (2007) Sterol biosynthesis inhibitors: potential for transition state analogs and mechanism-based inactivators targeted at sterol methyltransferase. Lipids 42:15-33
Lepesheva, Galina I; Zaitseva, Natalia G; Nes, W David et al. (2006) CYP51 from Trypanosoma cruzi: a phyla-specific residue in the B' helix defines substrate preferences of sterol 14alpha-demethylase. J Biol Chem 281:3577-85
Lepesheva, G I; Hargrove, T Y; Ott, R D et al. (2006) Biodiversity of CYP51 in trypanosomes. Biochem Soc Trans 34:1161-4
Nes, W D (2005) Enzyme redesign and interactions of substrate analogues with sterol methyltransferase to understand phytosterol diversity, reaction mechanism and the nature of the active site. Biochem Soc Trans 33:1189-96
Zhou, Wenxu; Song, Zhihong; Kanagasabai, Ragu et al. (2004) Mechanism-based enzyme inactivators of phytosterol biosynthesis. Molecules 9:185-203
Kanagasabai, Ragu; Zhou, Wenxu; Liu, Jialin et al. (2004) Disruption of ergosterol biosynthesis, growth, and the morphological transition in Candida albicans by sterol methyltransferase inhibitors containing sulfur at C-25 in the sterol side chain. Lipids 39:737-46
Lepesheva, Galina I; Nes, W David; Zhou, Wenxu et al. (2004) CYP51 from Trypanosoma brucei is obtusifoliol-specific. Biochemistry 43:10789-99
Nes, W David; Jayasimha, Pruthvi; Zhou, Wenxu et al. (2004) Sterol methyltransferase: functional analysis of highly conserved residues by site-directed mutagenesis. Biochemistry 43:569-76

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