Ketosteroid isomerase sequence

Fellow, Society for Risk Analysis

Outstanding Service Award, Society for Risk Analysis, 2012

Senior Fellow, Department of Epidemiology, University of Washington, 1976–1977

Postdoctoral Fellow, Departments of Pharmacology and Biophysics, Johns Hopkins Medical School, Baltimore, Maryland, 1966-1968

Elected Member, American Epidemiological Society

Distinguished Achievement Award, Society for Risk Analysis, 2001

Founders’ Award, Chemical Industry Institute of Toxicology, 1990

Lester R. Ford Award of Mathematical Association of America, 1977

Faculty Research Fellowship of Indiana University, 1974–1976

AB - Ketosteroid isomerase (KSI) from Comamonas testosteroni is a homodimeric enzyme with 125 amino acids in each monomer catalyzing the allylic isomerization reaction at rates comparable to the diffusion limit. Kinetic analysis of KSI refolding has been carried out to understand its folding mechanism. The refolding process as monitored by fluorescence change revealed that the process consists of three steps with a unimolecular fast, a bimolecular intermediate, and most likely unimolecular slow phases. The fast refolding step might involve the formation of structured monomers with hydrophobic surfaces that seem to have a high binding capacity for the amphipathic dye 8-anilino-1-naphthalenesulfonate. During the refolding process, KSI also generated a state that can bind equilenin, a reaction intermediate analogue, at a very early stage. These observations suggest that the KSI folding might be driven by the formation of the apolar active-site cavity while exposing hydrophobic surfaces. Since the monomeric folding intermediate may contain more than 83% of the native secondary structures as revealed previously, it is nativelike taking on most of the properties of the native protein. Urea-dependence analysis of refolding revealed the existence of folding intermediates for both the intermediate and slow steps. These steps were accelerated by cyclophilin A, a prolyl isomerase, suggesting the involvement of a cis-trans isomerization as a rate-limiting step. Taken together, we suggest that KSI folds into a monomeric intermediate, which has nativelike secondary structure, an apolar active site, and exposed hydrophobic surface, followed by dimerization and prolyl isomerizations to complete the folding.

Ketosteroid isomerase sequence

ketosteroid isomerase sequence


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