1b9i
From Proteopedia
CRYSTAL STRUCTURE OF 3-AMINO-5-HYDROXYBENZOIC ACID (AHBA) SYNTHASE
Structural highlights
Function[RIFK_AMYMS] Catalyzes the dehydration and aromatization of 5-amino-5-deoxy-3-dehydroshikimate (aminoDHS) to 3-amino-5-hydroxybenzoate (AHBA), a compound that then serves as the starter unit for the assembly of a polyketide during the biosynthesis of rifamycin B and other ansamycin antibiotics. Can not utilize 5-deoxy-5-amino-3-dehydroquinate (aminoDHQ), 5-deoxy-5-aminoshikimate (aminoSA), quinate, 3-dehydroquinate, or 3-dehydroshikimate (DHS) as substrate.[1] In a complex with RifL, RifK may have a second function in the AHBA pathway, acting as a transaminase introducing the nitrogen into the first pathway intermediate, UDP-3-keto-D-glucose, to give UDP-kanosamine. Appears to use glutamine as the nitrogen donor; NH(4)+ or asparagine are 30% less effective as nitrogen donors and neither glutamate nor aspartate show activity.[2] 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 PubMedThe biosynthesis of ansamycin antibiotics, including rifamycin B, involves the synthesis of an aromatic precursor, 3-amino-5-hydroxybenzoic acid (AHBA), which serves as starter for the assembly of the antibiotics' polyketide backbone. The terminal enzyme of AHBA formation, AHBA synthase, is a dimeric, pyridoxal 5'-phosphate (PLP) dependent enzyme with pronounced sequence homology to a number of PLP enzymes involved in the biosynthesis of antibiotic sugar moieties. The structure of AHBA synthase from Amycolatopsis mediterranei has been determined to 2.0 A resolution, with bound cofactor, PLP, and in a complex with PLP and an inhibitor (gabaculine). The overall fold of AHBA synthase is similar to that of the aspartate aminotransferase family of PLP-dependent enzymes, with a large domain containing a seven-stranded beta-sheet surrounded by alpha-helices and a smaller domain consisting of a four-stranded antiparallel beta-sheet and four alpha-helices. The uninhibited form of the enzyme shows the cofactor covalently linked to Lys188 in an internal aldimine linkage. On binding the inhibitor, gabaculine, the internal aldimine linkage is broken, and a covalent bond is observed between the cofactor and inhibitor. The active site is composed of residues from two subunits of AHBA synthase, indicating that AHBA synthase is active as a dimer. Crystal structure of 3-amino-5-hydroxybenzoic acid (AHBA) synthase.,Eads JC, Beeby M, Scapin G, Yu TW, Floss HG Biochemistry. 1999 Aug 3;38(31):9840-9. PMID:10433690[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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