Berlin 2012 – wissenschaftliches Programm
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BP: Fachverband Biologische Physik
BP 13: DNA/RNA and Related Enzymes
BP 13.1: Topical Talk
Mittwoch, 28. März 2012, 09:30–10:00, H 1058
Chemo-mechanics of a ring-shaped helicase during unwinding — •Michael Schlierf1,2, Ganggang Wang3, Xiaojiang Chen3, and Taekjip Ha1,4 — 1University of Illinois at Urbana-Champaign, Physics Department and Center for Physics of Living Cells, Urbana, Illinois — 2B CUBE - Center for Molecular Bioengineering, TU Dresden — 3University of Southern California, Department of Biological Sciences — 4Howard Hughes Medical Institute, Urbana, Illinois
Most replicative helicases are hexameric ring-shaped enzymes and are essential for cell survival. Despite extensive biochemical, structural and single-molecule investigations, how the translocation activities are utilized in the mechanical process of dsDNA unwinding are poorly understood. We investigated DnaB-family helicase G40P using a single molecule fluorescence-based unwinding assay with a single base pair resolution. The high-resolution assay revealed that G40P is an ultra-weak helicase that stalls at barriers as small as a single GC base pair and is a motor that moves with the step size of a single base pair. We directly observed the long-postulated activity of helicase slippage that is markedly enhanced under conditions that slow forward progression, but is fully suppressed by the primase DnaG.