1d0s: Difference between revisions
No edit summary |
No edit summary |
||
| Line 1: | Line 1: | ||
[[Image:1d0s.gif|left|200px]] | [[Image:1d0s.gif|left|200px]] | ||
<!-- | |||
The line below this paragraph, containing "STRUCTURE_1d0s", creates the "Structure Box" on the page. | |||
You may change the PDB parameter (which sets the PDB file loaded into the applet) | |||
or the SCENE parameter (which sets the initial scene displayed when the page is loaded), | |||
or leave the SCENE parameter empty for the default display. | |||
| | --> | ||
| | {{STRUCTURE_1d0s| PDB=1d0s | SCENE= }} | ||
}} | |||
'''CRYSTAL STRUCTURE OF NICOTINATE MONONUCLEOTIDE : 5,6-DIMETHYLBENZIMIDAZOLE PHOSPHORIBOSYLTRANSFERASE (COBT) FROM SALMONELLA TYPHIMURIUM COMPLEXED WITH 5, 6-DIMETHYLBENZIMIDAZOLE''' | '''CRYSTAL STRUCTURE OF NICOTINATE MONONUCLEOTIDE : 5,6-DIMETHYLBENZIMIDAZOLE PHOSPHORIBOSYLTRANSFERASE (COBT) FROM SALMONELLA TYPHIMURIUM COMPLEXED WITH 5, 6-DIMETHYLBENZIMIDAZOLE''' | ||
| Line 29: | Line 26: | ||
[[Category: Escalante-Semerena, J C.]] | [[Category: Escalante-Semerena, J C.]] | ||
[[Category: Rayment, I.]] | [[Category: Rayment, I.]] | ||
[[Category: | [[Category: Dinucleotide-binding motif]] | ||
[[Category: | [[Category: Phosphoribosyl transferase]] | ||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 13:19:12 2008'' | |||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | |||
Revision as of 13:19, 2 May 2008
CRYSTAL STRUCTURE OF NICOTINATE MONONUCLEOTIDE : 5,6-DIMETHYLBENZIMIDAZOLE PHOSPHORIBOSYLTRANSFERASE (COBT) FROM SALMONELLA TYPHIMURIUM COMPLEXED WITH 5, 6-DIMETHYLBENZIMIDAZOLE
OverviewOverview
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.
About this StructureAbout this Structure
1D0S is a Single protein structure of sequence from Salmonella typhimurium. Full crystallographic information is available from OCA.
ReferenceReference
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 Fri May 2 13:19:12 2008