Homo-timeric structural model of human microsomal prostaglandin E synthase-1 and characterization of its substrate/inhibitor binding interactions.
Inducible, microsomal prostaglandin E synthase 1 (mPGES-1), the terminal enzyme in the prostaglandin (PG) biosynthetic pathway, constitutes a promising therapeutic target for the development of new anti-inflammatory drugs. To elucidate structure-function relationships and to enable structure-based design, an mPGES-1 homology model was developed using the three-dimensional structure of the closest homologue of the MAPEG family (Membrane Associated Proteins in Eicosanoid and Glutathione metabolism), mGST-1. The ensuing model of mPGES-1 is a homo-trimer, with each monomer consisting of four membrane-spanning segments. Extensive structure refinement revealed an inter-monomer salt bridge (K26-E77) as well as inter-helical interactions within each monomer, including polar hydrogen bonds (e.g. T78-R110-T129) and hydrophobic pi-stacking (F82-F103-F106), all contributing to the overall stability of the homo-trimer of mPGES-1. Catalytic co-factor glutathione (GSH) was docked into the mPGES-1 model by flexible optimization of both the ligand and the protein conformations, starting from the initial location ascertained from the mGST-1 structure. Possible binding site for the substrate, prostaglandin H(2) (PGH(2)), was identified by systematically probing the refined molecular structure of mPGES-1. A binding model was generated by induced fit docking of PGH(2) in the presence of GSH. The homology model prescribes three potential inhibitor binding sites per mPGES-1 trimer. This was further confirmed experimentally by equilibrium dialysis study which generated a binding stoichiometric ratio of approximately three inhibitor molecules to three mPGES-1 monomers. The structural model that we have derived could serve as a useful tool for structure-guided design of inhibitors for this emergently important therapeutic target.
Xing
Li
L
Department of Structural and Computational Chemistry, St. Louis Laboratories, Pfizer Inc., 700 Chesterfield Parkway West, Chesterfield, MO 63017, USA. li.xing@pfizer.com
Kurumbail
Ravi G
RG
Frazier
Ronald B
RB
Davies
Michael S
MS
Fujiwara
Hideji
H
Weinberg
Robin A
RA
Gierse
James K
JK
Caspers
Nicole
N
Carter
Jeffrey S
JS
McDonald
Joseph J
JJ
Moore
William M
WM
Vazquez
Michael L
ML
D000595:Amino Acid Sequence; D001704:Biopolymers; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000494:pharmacology; D006801:Humans; D019746:Intramolecular Oxidoreductases / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D008861:Microsomes / Q000201:enzymology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D000071876:Prostaglandin-E Synthases; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid
D001704:Biopolymers; D004791:Enzyme Inhibitors; D019746:Intramolecular Oxidoreductases; C000605862:PTGES protein, human; D000071876:Prostaglandin-E Synthases
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