1ig0: Difference between revisions

[[Image:1ig0.gif|left|200px]]<br /><applet load="1ig0" size="350" color="white" frame="true" align="right" spinBox="true"  

BACKGROUND: Thiamin pyrophosphokinase (TPK) catalyzes the transfer of a pyrophosphate group from ATP to vitamin B1 (thiamin) to form the coenzyme thiamin pyrophosphate (TPP). Thus, TPK is important for the formation of a coenzyme required for central metabolic functions. TPK has no sequence homologs in the PDB and functions by an unknown mechanism. The TPK structure has been determined as a significant step toward elucidating its catalytic action. RESULTS: The crystal structure of Saccharomyces cerevisiae TPK complexed with thiamin has been determined at 1.8 A resolution. TPK is a homodimer, and each subunit consists of two domains. One domain resembles a Rossman fold with four alpha helices on each side of a 6 strand parallel beta sheet. The other domain has one 4 strand and one 6 strand antiparallel beta sheet, which form a flattened sandwich structure containing a jelly-roll topology. The active site is located in a cleft at the dimer interface and is formed from residues from domains of both subunits. The TPK dimer contains two compound active sites at the subunit interface. CONCLUSIONS: The structure of TPK with one substrate bound identifies the location of the thiamin binding site and probable catalytic residues. The structure also suggests a likely binding site for ATP. These findings are further supported by TPK sequence homologies. Although possessing no significant sequence homology with other pyrophospokinases, thiamin pyrophosphokinase may operate by a mechanism of pyrophosphoryl transfer similar to those described for pyrophosphokinases functioning in nucleotide biosynthesis.

1IG0 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Saccharomyces_cerevisiae Saccharomyces cerevisiae] with <scene name='pdbligand=VIB:'>VIB</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Thiamine_diphosphokinase Thiamine diphosphokinase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.7.6.2 2.7.6.2] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1IG0 OCA].  

[[Category: Baker, L J.]]

[[Category: Dorocke, J A.]]

[[Category: Harris, R A.]]

[[Category: Timm, D E.]]

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