Abstact

Genome sequencing projects have revealed that P-loop proteins are highly represented in all organisms and that many of them have no attributed function. They are characterized by a conserved nucleotide-binding domain and carry different activities implicated in many cellular processes. Saccharomyces cerevisiae YFH7 is one of these P-loop proteins of unknown function. In this work we tried to integrate bioinformatics, structure, and enzymology to discover the function of YFH7. Sequence analysis revealed that yeast YFH7 is a yeast-specific protein showing weak similarity with the phosphoribulokinase/uridine kinase/bacterial pantothenate kinase (PRK/URK/PANK) subfamily of P-loop containing kinases. A large insertion of about 100 residues distinguishes YFH7 from other members of the family. The 1.95 A resolution crystal structure of YFH7 solved using the SAD method confirmed that YFH7 has a fold similar to the PRK/URK/PANK family, with the characteristic core, lid, and NMP(bind) domains. An additional alpha/beta domain of novel topology corresponds to the large sequence insertion. Structural and ligand binding analysis combined with enzymatic assays suggest that YFH7 is an ATP-dependent small molecule kinase with new substrate specificity.