title: Regulation of translocation polarity by helicase domain 1 in SF2B helicases.
abstract: Structurally similar superfamily I (SF1) and II (SF2) helicases translocate on single-stranded DNA (ssDNA) with defined polarity either in the 5'-3' or in the 3'-5' direction. Both 5'-3' and 3'-5' translocating helicases contain the same motor core comprising two RecA-like folds. SF1 helicases of opposite polarity bind ssDNA with the same orientation, and translocate in opposite directions by employing a reverse sequence of the conformational changes within the motor domains. Here, using proteolytic DNA and mutational analysis, we have determined that SF2B helicases bind ssDNA with the same orientation as their 3'-5' counterparts. Further, 5'-3' translocation polarity requires conserved residues in HD1 and the FeS cluster containing domain. Finally, we propose the FeS cluster-containing domain also provides a wedge-like feature that is the point of duplex separation during unwinding.
authors.affiliation: Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Pugh
authors.forename: Colin G
authors.initials: CG
authors.lastname: Wu
authors.forename: Maria
authors.initials: M
authors.lastname: Spies
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D017124:Conserved Sequence; D004265:DNA Helicases / Q000737:chemistry* / Q000145:classification / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000737:chemistry / Q000378:metabolism; D004492:Edetic Acid / Q000031:analogs & derivatives / Q000737:chemistry; D007506:Iron-Sulfur Proteins / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009038:Motion; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship; D013822:Thermoplasma / Q000201:enzymology*
chemical_list: D004277:DNA, Single-Stranded; D007506:Iron-Sulfur Proteins; C042007:1-(4-bromoacetamidobenzyl)EDTA; D004492:Edetic Acid; D004265:DNA Helicases
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