Regensburg 2013 – scientific programme

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BP: Fachverband Biologische Physik

BP 25: Posters: Cytoskeleton

BP 25.21: Poster

Wednesday, March 13, 2013, 17:30–19:30, Poster C

Calmodulin regulates motility, dimerisation and phospholipid-binding of the unique myosin motor in Leishmania, myosin-XXI — •Christopher Batters, Heike Ellrich, Constanze Helbig, Katy Anne Woodall, Christian Hundschell, and Claudia Veigel — Division of Cellular Physiology and CeNS, LMU München, Schillerstrasse 44, 80336 München

The genome of the protozoan Leishmania parasite comprises just two classes of myosin, however only class XXI was shown to be expressed in both stages of the parasites life cycle. Apparently the only myosin motor in Leishmania, myosin-XXI is a unique model system and thought to perform a large variety of functions ranging from membrane anchorage to long-range directed cargo movement. However, nothing is known about the oligomerisation states, motility or cargo-binding of this motor. Using size exclusion chromatography, motility assays and electron microscopy we found that, in the absence of calmodulin, the motor formed immobile dimers. In the presence of calmodulin the motor was monomeric and moved actin filaments at ~15 nm.s-1. The monomers bound to liposomes, while the dimers did not. We identified phospholipid binding domains that overlapped with the dimerisation domains, including a PX-domain overlapping with the converter region. We propose a novel mechanism of myosin regulation where myosin-XXI monomers bind to lipid cargo and act as transporters, while the dimeric form is unable to bind to lipids and acts as an immobile, ATP-dependent crosslinker of actin filaments. Supported by SFB 863, CeNS, Baur-Stiftung