PNNL

Abstract

Using nuclear magnetic resonance (NMR) based methods including residual dipolar coupling restraints, we have determined the solution structure of the hypothetical Deinococcus radiodurans Nudix protein DR0079 (171 residues, MW = 19.3 kDa). The protein contains eight b-strands and three a-helices organized into three subdomains; an N-terminal b-sheet (1-34), a central Nudix core (35-140), and a C-terminal helix-turn-helix (141-171). The Nudix core and C-terminal helix-turn-helix form the fundamental fold common to the Nudix family, a large mixed b-sheet sandwiched between a-helices. The residues that compose the signature Nudix sequence, GX5EX7REUXEEXGU (where U = I, L, or V and X = any amino acid), are contained in a turn-helix-turn motif on the face of the mixed b-sheet. Chemical shift mapping experiments suggest that DR0079 binds Mg2+, but, precipitates out of solution in the presence of excess Mn2+. Experiments designed to determine the biological function of the protein indicate that it is not a type I isopentenyl-diphosphate d-isomerase and it does not bind a,b-methyleneadenosine 5’-triphosphate (AMPCPP) and guanosine 5’-[b,g-imido]triphosphate (GMPPNP). The structure of DR0079 is compared to other known Nudix protein structures, a potential substrate binding surface is proposed, and its possible biological function discussed.