Cytochromes P450 play a pivotal role in the detoxification and bioactivation of drugs, environmental contaminants, and numerous other foreign compounds. Under many conditions a single P450 may be exclusively or primarily responsible for the detoxification or bioactivation of a particular chemical. Accordingly, the phenotype of an individual human or experimental animal with respect to the amounts of particular P450 forms expressed in a given organ can determine the metabolism and pharmacological activity or toxicity of a compound. The long-term objective of the proposed research is to elucidate the molecular basis for the substrate specificity of cytochromes P450 2B. These enzymes represent the major phenobarbital-inducible cytochromes P450 in many species, and exhibit some striking differences as well as similarities in substrate specificity. To date, all individual amino acid residues that contribute to P450 2B specificity have been found within five of six proposed substrate recognition sites (SRSs). The hypothesis to be tested is that appropriate combinations of residue substitutions within the SRSs will interconvert the substrate specificities and susceptibility to inhibition of P450 2B enzymes. To address this hypothesis, wild-type and site-directed mutants of rat P450 2B1 and 2B2, rabbit P450 2B4 and 2B5, human P450 2B6, and canine P450 2B11 will be expressed in E. coli and analyzed with a battery of substrates and inhibitors. The results will be interpreted with the help of 3-D homology models based on bacterial cytochromes P450 of known structure. The individual specific aims are: 1) To identify inhibitors that distinguish between P450 2B1 and 2B2 and between P450 2B4 and 2B5 and to determine the amino acid residues responsible for the differences in selectivity. 2) To identify the structural basis for the unique functional properties of human P450 2B6 compared with its counterparts in other species. 3) To determine the mechanistic basis for differences in catalytic activity and inhibitor susceptibility of wild-type and mutant cytochromes P450 2B. The studies should provide a paradigm for predicting and/or rationalizing individual, strain, and species differences in P450 function.

Agency
National Institute of Health (NIH)
Institute
National Institute of Environmental Health Sciences (NIEHS)
Type
Research Project (R01)
Project #
7R01ES003619-15
Application #
2836734
Study Section
Pharmacology A Study Section (PHRA)
Project Start
1985-02-01
Project End
2003-01-31
Budget Start
1998-09-01
Budget End
1999-01-31
Support Year
15
Fiscal Year
1998
Total Cost
Indirect Cost
Name
University of Texas Medical Br Galveston
Department
Pharmacology
Type
Schools of Medicine
DUNS #
041367053
City
Galveston
State
TX
Country
United States
Zip Code
77555
Shah, Manish B; Zhang, Qinghai; Halpert, James R (2018) Crystal Structure of CYP2B6 in Complex with an Efavirenz Analog. Int J Mol Sci 19:
Chen, Chao; Liu, Jingbao; Halpert, James R et al. (2018) Use of Phenoxyaniline Analogues To Generate Biochemical Insights into the Interactio n of Polybrominated Diphenyl Ether with CYP2B Enzymes. Biochemistry 57:817-826
Shah, Manish B; Liu, Jingbao; Zhang, Qinghai et al. (2017) Halogen-? Interactions in the Cytochrome P450 Active Site: Structural Insights into Human CYP2B6 Substrate Selectivity. ACS Chem Biol 12:1204-1210
Shah, Manish B; Jang, Hyun-Hee; Wilderman, P Ross et al. (2016) Effect of detergent binding on cytochrome P450 2B4 structure as analyzed by X-ray crystallography and deuterium-exchange mass spectrometry. Biophys Chem 216:1-8
Liu, Jingbao; Shah, Manish B; Zhang, Qinghai et al. (2016) Coumarin Derivatives as Substrate Probes of Mammalian Cytochromes P450 2B4 and 2B6: Assessing the Importance of 7-Alkoxy Chain Length, Halogen Substitution, and Non-Active Site Mutations. Biochemistry 55:1997-2007
Shah, Manish B; Wilderman, P Ross; Liu, Jingbao et al. (2015) Structural and biophysical characterization of human cytochromes P450 2B6 and 2A6 bound to volatile hydrocarbons: analysis and comparison. Mol Pharmacol 87:649-59
Jang, Hyun-Hee; Liu, Jingbao; Lee, Ga-Young et al. (2015) Functional importance of a peripheral pocket in mammalian cytochrome P450 2B enzymes. Arch Biochem Biophys 584:61-9
Wilderman, P Ross; Jang, Hyun-Hee; Malenke, Jael R et al. (2014) Functional characterization of cytochromes P450 2B from the desert woodrat Neotoma lepida. Toxicol Appl Pharmacol 274:393-401
Jang, Hyun-Hee; Davydov, Dmitri R; Lee, Ga-Young et al. (2014) The role of cytochrome P450 2B6 and 2B4 substrate access channel residues predicted based on crystal structures of the amlodipine complexes. Arch Biochem Biophys 545:100-7
Shah, Manish B; Jang, Hyun-Hee; Zhang, Qinghai et al. (2013) X-ray crystal structure of the cytochrome P450 2B4 active site mutant F297A in complex with clopidogrel: insights into compensatory rearrangements of the binding pocket. Arch Biochem Biophys 530:64-72

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