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AKB: Biologische Physik

AKB 30: Poster Session I

AKB 30.24: Poster

Montag, 27. März 2006, 15:30–18:00, P1

Binding of TmHU to single ds-DNA observed by optical tweezers — •Mathias Salomo¹, Klaus Kroy¹, Kati Kegler¹, Christof Gutsche¹, Marc Struhalla², Jörg Reinmuth¹, Wiktor Skokov¹, Claudia Immisch³, and Friedrich Kremer¹ — ¹University of Leipzig — ²c-LEcta GmbH, Leipzig — ³ACGT Progenomics AG, Halle

We employed optical tweezers to study the binding and disruption of the histone-like protein TmHU (from Thermotoga maritima) on DNA at a single molecule level. For the binding reaction, a force-independent reaction rate was observed, in contrast to earlier findings for histone/DNA complex formation. This suggests that there are no force dependent kinetic barriers involved. For the disruption process, pronounced sawtooth like patterns were observed in the measured force-extension relation. The data were brought in direct relation to a microscopic model, which evaluates the energetics of the reaction based on the bending of the DNA in the course of interaction. It suggests that the independent binding of individual proteins to the DNA is kinetically delayed and explains the abrupt halt of the binding reaction at stretching forces of about 20-25 pN. It moreover provides compelling evidence for a (yet unknown) cooperative reaction mechanism.