2cfc
From Proteopedia
|
STRUCTURAL BASIS FOR STEREO SELECTIVITY IN THE (R)- AND (S)-HYDROXYPROPYLETHANE THIOSULFONATE DEHYDROGENASES
Overview
Epoxide metabolism in Xanthobacter autotrophicus Py2 results in the, conversion of epoxypropane to acetoacetate. Epoxide metabolism is, initiated by the nucleophilic addition of coenzyme M to the (R)- and, (S)-enantiomers of epoxypropane which forms the respective enantiomers of, 2-hydroxypropyl-coenyme M. The (R)- and (S)-enantiomers of 2-hydroxypropyl, coenzyme are oxidized to the achiral product 2-ketopropyl-CoM by two, stereoselective dehydrogenases. The dehydrogenases catalyzing these, reactions, termed (R)-hydroxypropyl-coenzyme M dehydrogenase (R-HPCDH) and, (S)-hydroxypropyl-coenzyme M dehydrogenase (S-HPCDH), are NAD(+)-dependent, enzymes belonging to the short chain dehydrogenase/reductase (SDR) family, of enzymes. In this study, the crystal structure of R-HPCDH cocrystallized, in the presence of (S)-hydroxypropyl-coenzyme M has been determined using, X-ray diffraction methods and refined to 1.8 A resolution. The structure, of R-HPCDH is tetrameric and stabilized by the interaction of the terminal, carboxylates of each subunit with divalent metal ions. The structure of, the presumed product-bound state reveals that binding interactions between, the negatively charged oxygen atoms of the sulfonate moiety have striking, similarities to sulfonate interactions observed in the previously, determined structure of 2-ketopropyl-CoM oxidoreductase/carboxylase, highlighting the utility of coenzyme M as a carrier molecule in the, pathway. The key elements of the aforementioned interactions are, electrostatic interactions between the sulfonate oxygen atoms and two, arginine residues (R152 and R196) of R-HPCDH. The comparison of the, structure of R-HPCDH with a homology model of S-HPCDH provides a, structural basis for a mechanism of substrate specificity in which the, binding of the substrate sulfonate moiety at distinct sites on each, stereoselective enzyme directs the orientation of the appropriate, substrate enantiomer for hydride abstraction.
About this Structure
2CFC is a Single protein structure of sequence from Xanthobacter autotrophicus with NAD and KPC as ligands. Active as 2-(R)-hydroxypropyl-CoM dehydrogenase, with EC number 1.1.1.268 Known structural/functional Site: . Full crystallographic information is available from OCA.
Reference
Structural basis for stereoselectivity in the (R)- and (S)-hydroxypropylthioethanesulfonate dehydrogenases., Krishnakumar AM, Nocek BP, Clark DD, Ensign SA, Peters JW, Biochemistry. 2006 Jul 25;45(29):8831-40. PMID:16846226
Page seeded by OCA on Tue Dec 18 19:20:14 2007
