Display Settings:

Format

Send to:

Choose Destination
J Biol Chem. 2001 Mar 30;276(13):10358-65. Epub 2000 Dec 19.

Mutational and X-ray crystallographic analysis of the interaction of dihomo-gamma -linolenic acid with prostaglandin endoperoxide H synthases.

Author information

  • 1Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824, USA.

Abstract

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.

PMID:
11121413
[PubMed - indexed for MEDLINE]
Free full text

LinkOut - more resources

Full Text Sources

Other Literature Sources

Molecular Biology Databases

PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Icon for HighWire
    Loading ...
    Write to the Help Desk