4thi
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THIAMINASE I FROM BACILLUS THIAMINOLYTICUS WITH COVALENTLY BOUND 4-AMINO-2,5-DIMETHYLPYRIMIDINE
OverviewOverview
Thiaminase-I catalyzes the replacement of the thiazole moiety of thiamin, with a wide variety of nucleophiles, such as pyridine, aniline, catechols, quinoline, and cysteine. The crystal structure of the enzyme from Bacillus, thiaminolyticus was determined at 2.5 A resolution by multiple isomorphous, replacement and refined to an R factor of 0.195 (Rfree = 0.272). Two other, structures, one native and one containing a covalently bound inhibitor, were determined at 2.0 A resolution by molecular replacement from a second, crystal form and were refined to R factors of 0.205 and 0.217 (Rfree =, 0.255 and 0.263), respectively. The overall structure contains two, alpha/beta-type domains separated by a large cleft. At the base of the, cleft lies Cys113, previously identified as a key active site nucleophile., The structure with a covalently bound thiamin analogue, which functions as, a mechanism-based inactivating agent, confirms the location of the active, site. Glu241 appears to function as an active site base to increase the, nucleophilicity of Cys113. The mutant Glu241Gln was made and shows no, activity. Thiaminase-I shows no sequence identity to other proteins in the, sequence databases, but the three-dimensional structure shows very high, structural homology to the periplasmic binding proteins and the, transferrins.
About this StructureAbout this Structure
4THI is a Single protein structure of sequence from Bacillus subtilis with SO4 and PYD as ligands. Active as Thiamine pyridinylase, with EC number 2.5.1.2 Full crystallographic information is available from OCA.
ReferenceReference
Crystal structure of thiaminase-I from Bacillus thiaminolyticus at 2.0 A resolution., Campobasso N, Costello CA, Kinsland C, Begley TP, Ealick SE, Biochemistry. 1998 Nov 10;37(45):15981-9. PMID:9843405
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