NEW INSIGHTS FOR DINUCLEOTIDE BACKBONE BINDING IN CONSERVED C5'-H-CENTER-DOT-CENTER-DOT-CENTER-DOT-O HYDROGEN-BONDS

Most enzymes that utilize dinucleotide NAD or NADP are known to compri se a glycine-rich loop segment (e.g. the GXGXXG signature motif of Ros sman fold) which binds the cofactor's diphosphate moiety. Through anal ysis of a set of diverse NAD(P)-bound protein structures, we show here that with few exceptions this diphosphate binding is complemented by a second loop segment interacting from a different angle with unconven tional yet apparently ubiquitous C-H...O hydrogen bonds formed between C5' methylene of dinucleotide and, primarily, carbonyl oxygen of prot ein. This finding implicates an important role of C5' in protein-nucle otide recognition. (C) 1998 Academic Press Limited.