1fe2
CRYSTAL STRUCTURE OF DIHOMO-GAMMA-LINOLEIC ACID BOUND IN THE CYCLOOXYGENASE CHANNEL OF PROSTAGLANDIN ENDOPEROXIDE H SYNTHASE-1.
|
OverviewOverview
Prostaglandin endoperoxide H synthases-1 and -2 (PGHSs) catalyze the, committed step in prostaglandin biosynthesis. Both isozymes can oxygenate, a variety of related polyunsaturated fatty acids. We report here the x-ray, crystal structure of dihomo-gamma-linolenic acid (DHLA) in the, cyclooxygenase site of PGHS-1 and the effects of active site substitutions, on the oxygenation of DHLA, and we compare these results to those obtained, previously with arachidonic acid (AA). DHLA is bound within the, cyclooxygenase site in the same overall L-shaped conformation as AA. C-1, and C-11 through C-20 are in the same positions for both substrates, but, the positions of C-2 through C-10 differ by up to 1.74 A. In general, substitutions of active site residues caused parallel changes in the, oxygenation of both AA and DHLA. Two significant exceptions were Val-349, and Ser-530. A V349A substitution caused an 800-fold decrease in the, V(max)/K(m) for DHLA but less than a 2-fold change with AA; kinetic, evidence indicates that C-13 of DHLA is improperly positioned with respect, to Tyr-385 in the V349A mutant thereby preventing efficient hydrogen, abstraction. Val-349 contacts C-5 of DHLA and appears to serve as a, structural bumper positioning the carboxyl half of DHLA, which, in turn, positions properly the omega-half of this substrate. A V349A substitution, in PGHS-2 has similar, minor effects on the rates of oxygenation of AA and, DHLA. Thus, Val-349 is a major determinant of substrate specificity for, PGHS-1 but not for PGHS-2. Ser-530 also influences the substrate, specificity of PGHS-1; an S530T substitution causes 40- and 750-fold, decreases in oxygenation efficiencies for AA and DHLA, respectively.
About this StructureAbout this Structure
1FE2 is a Single protein structure of sequence from Ovis aries with BOG, COH and LAX as ligands. Active as D-amino-acid dehydrogenase, with EC number 1.4.99.1 Full crystallographic information is available from OCA.
ReferenceReference
Mutational and X-ray crystallographic analysis of the interaction of dihomo-gamma -linolenic acid with prostaglandin endoperoxide H synthases., Thuresson ED, Malkowski MG, Lakkides KM, Rieke CJ, Mulichak AM, Ginell SL, Garavito RM, Smith WL, J Biol Chem. 2001 Mar 30;276(13):10358-65. Epub 2000 Dec 19. PMID:11121413
Page seeded by OCA on Mon Nov 12 16:52:16 2007