NBP35 ENCODES AN ESSENTIAL AND EVOLUTIONARY CONSERVED PROTEIN IN SACCHAROMYCES-CEREVISIAE WITH HOMOLOGY TO A SUPERFAMILY OF BACTERIAL ATPASES

We have cloned a novel and essential gene, NBP35, from Saccharomyces c erevisiae that encodes a putative Nucleotide Binding Protein of 35 kDa . Sequence analysis revealed structural homology of Nbp35p with a fami ly of bacterial ATPases involved in cell division processes and chromo some partitioning. A search in databases identified closely related se quences from yeast and higher eukaryotes, suggesting a conserved funct ion for this family of proteins. By indirect immunofluorescence, a tag ged version of Nbp35p carrying two immunoglobulin G-binding domains de rived from Staphylococcus aureus Protein A was localised to the nucleu s. A single amino-acid substitution in the conserved nucleotide-bindin g motif of Nbp35p renders the protein non-functional. Furthermore, a c onserved cluster of four cysteines in the N-terminal end of the protei n is also required for an essential role of Nbp35p.