title: Dbp9p, a member of the DEAD box protein family, exhibits DNA helicase activity.
abstract: The yeast Dbp9p is a member of the DEAD box family of RNA helicases, which are thought to be involved in RNA metabolism. Dbp9p seems to function in ribosomal RNA biogenesis, but it has not been biochemically characterized. To analyze the enzymatic characteristics of the protein, we expressed a recombinant Dbp9p in Escherichia coli and purified it to homogeneity. The purified protein exhibited RNA unwinding and binding activity in the absence of NTP, and this activity was abolished by a mutation in the RNA-binding domain. We then characterized the ATPase activity of Dbp9p with respect to cofactor specificity; the activity was found to be severely inhibited by yeast total RNA and moderately inhibited by poly(U), poly(A), and poly(C) but to be stimulated by yeast genomic DNA and salmon sperm DNA. In addition, Dbp9p exhibited DNA-DNA and DNA-RNA helicase activity in the presence of ATP. These results indicate that Dbp9p has biochemical characteristics unique among DEAD box proteins.
authors.affiliation: Department of Biological Science and Technology, Faculty of Industrial Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda-shi, Chiba 278-8510, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Kikuma
authors.forename: Masaya
authors.initials: M
authors.lastname: Ohtsu
authors.forename: Takahiko
authors.initials: T
authors.lastname: Utsugi
authors.forename: Shoko
authors.initials: S
authors.lastname: Koga
authors.forename: Kohji
authors.initials: K
authors.lastname: Okuhara
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Eki
authors.forename: Fumihiro
authors.initials: F
authors.lastname: Fujimori
authors.forename: Yasufumi
authors.initials: Y
authors.lastname: Murakami
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D001483:Base Sequence; D053487:DEAD-box RNA Helicases; D004265:DNA Helicases / Q000302:isolation & purification / Q000378:metabolism*; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000187:drug effects / Q000378:metabolism; D007700:Kinetics; D009687:Nuclear Proteins / Q000302:isolation & purification / Q000378:metabolism*; D020365:RNA Helicases / Q000302:isolation & purification / Q000378:metabolism*; D012331:RNA, Fungal / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: C436685:DBP9 protein, S cerevisiae; D004271:DNA, Fungal; D004277:DNA, Single-Stranded; D009687:Nuclear Proteins; D012331:RNA, Fungal; D029701:Saccharomyces cerevisiae Proteins; D000251:Adenosine Triphosphatases; D004265:DNA Helicases; D053487:DEAD-box RNA Helicases; D020365:RNA Helicases