1SZO

Crystal Structure Analysis of the 6-Oxo Camphor Hydrolase His122Ala Mutant Bound to Its Natural Product (2S,4S)-alpha-Campholinic Acid

Summary for 1SZO

• Entry DOI: 10.2210/pdb1szo/pdb
• Related: 1DUB 1O8U
• Descriptor: 6-oxocamphor hydrolase, (2S,4S)-4-(2,2-DIHYDROXYETHYL)-2,3,3-TRIMETHYLCYCLOPENTANONE, CALCIUM ION, ... (4 entities in total)
• Functional Keywords: enzyme-product complex, hydrolase
• Biological source: Rhodococcus sp. NCIMB 9784
• Total number of polymer chains: 12
• Total formula weight: 343749.35

Authors

Leonard, P.M.,Grogan, G. (deposition date: 2004-04-06, release date: 2004-06-29, Last modification date: 2023-08-23)

Primary citation

Leonard, P.M.,Grogan, G.
Structure of 6-oxo camphor hydrolase H122A mutant bound to its natural product, (2S,4S)-alpha-campholinic acid: mutant structure suggests an atypical mode of transition state binding for a crotonase homolog.
J.Biol.Chem., 279:31312-31317, 2004

PubMed Abstract: The crotonase homolog, 6-oxo camphor hydrolase (OCH), catalyzes the desymmetrization of bicyclic beta-diketones to optically active keto acids via an enzymatic retro-Claisen reaction, resulting in the cleavage of a carbon-carbon bond. We have previously reported the structure of OCH (Whittingham, J. L., Turkenburg, J. P., Verma, C. S., Walsh, M. A., and Grogan, G. (2003) J. Biol. Chem. 278, 1744-1750), which suggested the involvement of five residues, His-45, His-122, His-145, Asp-154, and Glu-244, in catalysis. Here we report mutation studies on OCH that reveal that H145A and D154N mutants of OCH have greatly reduced values of k(cat)/K(m) derived from a very large increase in K(m) for the native substrate, 6-oxo camphor. In addition, H122A has a greatly reduced value of k(cat), and its K(m) is five times that of the wild-type. The location of the active site is confirmed by the 1.9-A structure of the H122A mutant of OCH complexed with the minor diastereoisomer of (2S,4S)-alpha-campholinic acid, the natural product of the enzyme. This shows the pendant acetate of the product hydrogen bonded to a His-145/Asp-154 dyad and the endocyclic carbonyl of the cyclopentane ring hydrogen bonded to Trp-40. The results are suggestive of a base-catalyzed mechanism of C-C bond cleavage and provide clues to the origin of prochiral selectivity by the enzyme and to the recruitment of the crotonase fold for alternate modes of transition state stabilization to those described for other crotonase superfamily members.

PubMed: 15138275
DOI: 10.1074/jbc.M403514200

Experimental method

X-RAY DIFFRACTION (1.9 Å)