Steve Ealick's Research Group

Abstract:

Chatterjee A, Li S, Zhang Y, Grove TL, Lee M, Krebs C, Booker SJ, and Begley TP, and Ealick SE. Reconstitution of ThiC in thiamine pyrimidine biosynthesis expands the radical SAM superfamily. Nat. Chem. Biol. 4, 758-765 (2008).

4-Amino-5-hydroxymethyl-2-methylpyrimidine phosphate (HMP-P) synthase catalyzes a complex rearrangement of 5-aminoimidazole ribonucleotide (AIR) to form  HMP-P, the pyrimidine moiety of thiamin phosphate.  The three-dimensional structures of HMP-P synthase and its complexes with the product HMP-P and a substrate analog imidazole ribotide were determined.  The structure of HMP-P synthase reveals a homodimer in which each protomer comprises three domains: an N-terminal domain with a novel fold, a central (ba )₈  barrel and a disordered C-terminal domain that contains a conserved CX2CX4C motif, suggestive of [4Fe-4S] cluster.  Biochemical studies have confirmed that HMP-P synthase is iron sulfur cluster dependent, that it is a novel member of the radical SAM superfamily and that HMP-P and 5′-deoxyadenosine are products of the reaction. Mössbauer and EPR spectroscopy confirm the presence of one [4Fe-4S] cluster.  Structural comparisons reveal that HMP-P synthase is homologous to a group of adenosylcobalamin radical enzymes.  This similarity supports an evolutionary relationship between these two superfamilies.