1ka9
From Proteopedia
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Imidazole Glycerol Phosphate Synthase
Overview
Imidazole glycerol phosphate synthase (IGPs) catalyzes the fifth step in, the histidine biosynthetic pathway located at the branch point to de novo, purine biosynthesis. IGPs is a multienzyme comprising glutaminase and, synthase subunits. The glutaminase activity, which hydrolyzes glutamine to, give ammonia, is coupled with substrate binding to the synthase subunit., The three-dimensional structure of the IGPs from Thermus thermophilus HB8, has been determined at 2.3 A resolution, and compared with the previously, determined structures for the yeast and Thermotoga maritima enzymes. The, structure of each subunit is similar to that of the corresponding domain, in the yeast enzyme or subunit in the T. maritima enzyme. However, the, overall structure is significantly different from the yeast and T., maritima enzymes, indicating that IGPs may change the relative orientation, between the two subunits and close the glutaminase site upon glutamine, binding. The putative ammonia tunnel, which carries nascent ammonia from, glutaminase to the synthase site, has a closed gate comprising a cyclic, salt bridge formed by four charged residues of the synthase subunit. The, side chain of Lys100 in the cyclic salt bridge might change its side chain, direction to form new interactions with the main chain carbonyl group of, glutamine from the synthase subunit and the hydoxyl group of tyrosine from, the glutaminase subunit, resulting in the opening of the gate for ammonia, transfer.
About this Structure
1KA9 is a Protein complex structure of sequences from Thermus thermophilus. Full crystallographic information is available from OCA.
Reference
Structure of imidazole glycerol phosphate synthase from Thermus thermophilus HB8: open-closed conformational change and ammonia tunneling., Omi R, Mizuguchi H, Goto M, Miyahara I, Hayashi H, Kagamiyama H, Hirotsu K, J Biochem (Tokyo). 2002 Nov;132(5):759-65. PMID:12417026
Page seeded by OCA on Tue Nov 20 18:59:44 2007
