1ogz
From Proteopedia
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CRYSTAL STRUCTURE OF 5-3-KETOSTEROID ISOMERASE MUTANTS P39A COMPLEXED WITH EQUILENIN FROM PSEUDOMONAS TESTOSTERONI
Overview
KSI (ketosteroid isomerase) from Comamonas testosteroni is a homodimeric, enzyme that catalyses the allylic isomerization of Delta5-3-ketosteroids, to their conjugated Delta4-isomers at a reaction rate equivalent to the, diffusion-controlled limit. Based on the structural analysis of KSI at a, high resolution, the conserved cis-Pro39 residue was proposed to be, involved in the proper positioning of Asp38, a critical catalytic residue, since the residue was found not only to be structurally associated with, Asp38, but also to confer a structural rigidity on the local active-site, geometry consisting of Asp38, Pro39, Val40, Gly41 and Ser42 at the, flexible loop between b-strands B1 and B2. In order to investigate the, structural role of the conserved cis-Pro39 residue near the active site of, KSI, Pro39 was replaced with alanine or glycine. The free energy of, activation for the P39A and P39G mutants increased by 10.5 and 16.7 kJ/mol, (2.5 and 4.0 kcal/mol) respectively, while DG(U)H2O (the free-energy, change for unfolding in the absence of urea at 25.00+/-0.02 degrees C), decreased by 31.0 and 35.6 kJ/mol (7.4 and 8.5 kcal/mol) respectively, compared with the wild-type enzyme. The crystal structure of the P39A, mutant in complex with d-equilenin, [d-1,3,5(10),6,8-estrapentaen-3-ol-17-one], a reaction intermediate, analogue, determined at 2.3 A (0.23 nm) resolution revealed that the P39A, mutation significantly disrupted the proper orientations of both, d-equilenin and Asp38, as well as the local active-site geometry near, Asp38, which resulted in substantial decreases in the activity and, stability of KSI. Upon binding 1-anilinonaphthalene-8-sulphonic acid, the, fluorescence intensities of the P39A and P39G mutants were increased, drastically, with maximum wavelengths blue-shifted upon binding, indicating that the mutations might alter the hydrophobic active site of, KSI. Taken together, our results demonstrate that the conserved cis-Pro39, residue plays a crucial role in the proper positioning of the critical, catalytic base Asp38 and in the structural integrity of the active site in, KSI.
About this Structure
1OGZ is a Single protein structure of sequence from Comamonas testosteroni with EQU as ligand. Active as Steroid Delta-isomerase, with EC number 5.3.3.1 Known structural/functional Site: . Full crystallographic information is available from OCA.
Reference
The conserved cis-Pro39 residue plays a crucial role in the proper positioning of the catalytic base Asp38 in ketosteroid isomerase from Comamonas testosteroni., Nam GH, Cha SS, Yun YS, Oh YH, Hong BH, Lee HS, Choi KY, Biochem J. 2003 Oct 15;375(Pt 2):297-305. PMID:12852789
Page seeded by OCA on Tue Dec 18 17:42:57 2007
