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CRYSTAL STRUCTURE OF PORPHOBILINOGEN SYNTHASE COMPLEXED WITH THE INHIBITOR 4,7-DIOXOSEBACIC ACID
Structural highlights
FunctionHEM2_ECOLI Catalyzes an early step in the biosynthesis of tetrapyrroles. Binds two molecules of 5-aminolevulinate per subunit, each at a distinct site, and catalyzes their condensation to form porphobilinogen. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed4,7-Dioxosebacic acid (4,7-DOSA) is an active site-directed irreversible inhibitor of porphobilinogen synthase (PBGS). PBGS catalyzes the first common step in the biosynthesis of the tetrapyrrole cofactors such as heme, vitamin B(12), and chlorophyll. 4,7-DOSA was designed as an analogue of a proposed reaction intermediate in the physiological PBGS-catalyzed condensation of two molecules of 5-aminolevulinic acid. As shown here, 4,7-DOSA exhibits time-dependent and dramatic species-specific inhibition of PBGS enzymes. IC(50) values vary from 1 microM to 2.4 mM for human, Escherichia coli, Bradyrhizobium japonicum, Pseudomonas aeruginosa, and pea enzymes. Those PBGS utilizing a catalytic Zn(2+) are more sensitive to 4,7-DOSA than those that do not. Weak inhibition of a human mutant PBGS establishes that the inactivation by 4,7-DOSA requires formation of a Schiff base to a lysine that normally forms a Schiff base intermediate to one substrate molecule. A 1.9 A resolution crystal structure of E. coli PBGS complexed with 4,7-DOSA (PDB code ) shows one dimer per asymmetric unit and reveals that the inhibitor forms two Schiff base linkages with each monomer, one to the normal Schiff base-forming Lys-246 and the other to a universally conserved "perturbing" Lys-194 (E. coli numbering). This is the first structure to show inhibitor binding at the second of two substrate-binding sites. Mechanistic basis for suicide inactivation of porphobilinogen synthase by 4,7-dioxosebacic acid, an inhibitor that shows dramatic species selectivity.,Kervinen J, Jaffe EK, Stauffer F, Neier R, Wlodawer A, Zdanov A Biochemistry. 2001 Jul 27;40(28):8227-36. PMID:11444968[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences | ||||||||||||||||||||
