BIOCHEMICAL AND GENETIC-CHARACTERIZATION OF A REPLICATION PROTEIN-A DEPENDENT DNA HELICASE FROM THE YEAST, SACCHAROMYCES-CEREVISIAE

We have purified a DNA dependent ATPase/DNA helicase, DNA helicase B, from S. cerevisiae. Helicase B was a 129-kDa polypeptide. The ATPase a ctivity of helicase B was strongly DNA dependent. The DNA helicase act ivity was stimulated by yeast replication protein A,indicating a proba ble function in DNA replication. Helicase B showed a 5'-->3' polarity of movement. Protein sequencing indicated that helicase B was identica l to a hypothetical 127-kDa polypeptide encoded by yORF61, located 5' upstream of the BMH1 locus in chromosome v. The protein sequence conta ined a ''type I ATP/GTP binding motif'' and other helicase-like motifs and the expressed protein exhibited helicase activity. Thus, we concl uded that yORF61 is the gene for helicase B and will be referred to as HCSB. (C) 1995 Academic Press. Inc.