Regensburg 2010 – scientific programme

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BP: Fachverband Biologische Physik

BP 7: Posters: Biological Machines, Motor Proteins

BP 7.6: Poster

Monday, March 22, 2010, 17:15–20:00, Poster B1

Direct observation of the myosin-V power stroke and its reversal — •James R. Sellers³ and Claudia Veigel^1,2 — ¹Abteilung Zellulaere Physiologie, Institut fuer Physiologie, Ludwig Maximilians Universitaet Muenchen, Pettenkoferstrasse 12, Muenchen, Germany — ²Physical Biochemistry, National Institute for Medical Research, The Ridgeway Mill Hill, London NW7 1AA, UK — ³Laboratory of Molecular Physiology, National Heart, Lung and Blood Institute, NIH, Bethesda, MD USA 20892

Complex forms of cellular motility, including cell division, organelle trafficking or signal amplification in the auditory system, require strong coordination of the myosin motors involved. The most basic mechanism of coordination is direct mechanical interactions of individual motors that modifies their mechano-chemical cycles. Here, we used an optical tweezers-based single molecule assay to investigate the reversibility of the force generating conformational change (power stroke) of single myosin-V motor heads. By applying load to the head shortly after binding to actin, we found that at a certain load, the power stroke could be reversed. At this load the motor fluctuated between an actin-bound pre- and a post-power stroke conformation. This dramatic, load-dependent mechanical instability of a single motor head might be critical to coordinate the heads of processive, dimeric myosin-V. Interestingly, highly non-linear response to load, such as power stroke reversal, can lead to coordination, synchronisation or even oscillations already amongst motors alone. These phenomena are critical for many cellular functions.