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| | {{STRUCTURE_1d0v| PDB=1d0v | SCENE= }} | | {{STRUCTURE_1d0v| PDB=1d0v | SCENE= }} |
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| - | '''CRYSTAL STRUCTURE OF NICOTINATE MONONUCLEOTIDE:5,6-DIMETHYLBENZIMIDAZOLE PHOSPHORIBOSYLTRANSFERASE (COBT) FROM SALMONELLA TYPHIMURIUM COMPLEXED WITH ITS REACTION PRODUCTS DETERMINED TO 1.9 A RESOLUTION'''
| + | ===CRYSTAL STRUCTURE OF NICOTINATE MONONUCLEOTIDE:5,6-DIMETHYLBENZIMIDAZOLE PHOSPHORIBOSYLTRANSFERASE (COBT) FROM SALMONELLA TYPHIMURIUM COMPLEXED WITH ITS REACTION PRODUCTS DETERMINED TO 1.9 A RESOLUTION=== |
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| - | ==Overview==
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| - | Nicotinate mononucleotide:5,6-dimethylbenzimidazole phosphoribosyltransferase (CobT) from Salmonella typhimurium plays a central role in the synthesis of alpha-ribazole, which is a key component of the lower ligand of cobalamin. Two X-ray structures of CobT are reported here at 1.9 A resolution. First, a complex of CobT with 5,6-dimethylbenzimidazole, and second, a complex of CobT with its reaction products, nicotinate and alpha-ribazole-5'-phosphate. CobT was cocrystallized with 5,6-dimethylbenzimidazole (DMB) in the space group P2(1)2(1)2 with unit cell dimensions of a = 72.1 A, b = 90.2 A, and c = 47.5 A and one protomer per asymmetric unit. Subsequently, the crystals containing DMB were soaked in nicotinate mononucleotide whereupon the physiological reaction occurred in the crystal lattice to yield nicotinate and alpha-ribazole-5'-phosphate. These studies show that CobT is a dimer where each subunit consists of two domains. The large domain is dominated by a parallel six-stranded beta-sheet with connecting alpha-helices that exhibit the topology of a Rossmann fold. The small domain is made from components of the N- and C-terminal sections of the polypeptide chain and contains a three-helix bundle. The fold of CobT is unrelated to the type I and II phosphoribosylpyrophosphate dependent transferases and does not appear to be related to any other protein whose structure is known. The enzyme active site is located in a large cavity formed by the loops at the C-terminal ends of the beta-strands and the small domain of the neighboring subunit. DMB binds in a hydrophobic pocket created in part by the neighboring small domain. This is consistent with the broad specificity of this enzyme for aromatic substrates [Trzebiatowski, J. R., Escalante-Semerena (1997) J. Biol. Chem. 272, 17662-17667]. The binding site for DMB suggests that Glu317 is the catalytic base required for the reaction. The remainder of the cavity binds the nicotinate and ribose-5'-phosphate moieties, which are nestled within the loops at the ends of the beta-strands. Interestingly, the orientation of the substrate and products are opposite from that expected for a Rossmann fold.
| + | The line below this paragraph, {{ABSTRACT_PUBMED_10587435}}, adds the Publication Abstract to the page |
| | + | (as it appears on PubMed at http://www.pubmed.gov), where 10587435 is the PubMed ID number. |
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| | + | {{ABSTRACT_PUBMED_10587435}} |
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| | ==About this Structure== | | ==About this Structure== |
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| | [[Category: Dinucleotide-binding motif]] | | [[Category: Dinucleotide-binding motif]] |
| | [[Category: Phosphoribosyltransferase]] | | [[Category: Phosphoribosyltransferase]] |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 13:19:23 2008'' | + | |
| | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jun 30 21:58:34 2008'' |
Revision as of 18:58, 30 June 2008
Template:STRUCTURE 1d0v
CRYSTAL STRUCTURE OF NICOTINATE MONONUCLEOTIDE:5,6-DIMETHYLBENZIMIDAZOLE PHOSPHORIBOSYLTRANSFERASE (COBT) FROM SALMONELLA TYPHIMURIUM COMPLEXED WITH ITS REACTION PRODUCTS DETERMINED TO 1.9 A RESOLUTION
Template:ABSTRACT PUBMED 10587435
About this Structure
1D0V is a Single protein structure of sequence from Salmonella typhimurium. Full crystallographic information is available from OCA.
Reference
The three-dimensional structures of nicotinate mononucleotide:5,6- dimethylbenzimidazole phosphoribosyltransferase (CobT) from Salmonella typhimurium complexed with 5,6-dimethybenzimidazole and its reaction products determined to 1.9 A resolution., Cheong CG, Escalante-Semerena JC, Rayment I, Biochemistry. 1999 Dec 7;38(49):16125-35. PMID:10587435
Page seeded by OCA on Mon Jun 30 21:58:34 2008
