Expression Studies of Other Unconventional Myosins

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In collaboration with Philipp Kukura of Oxford University, we have used a light microscopy based interferometric scattering technique to examine the processive movement of myosin 5 HMM on actin. By attaching a 20 nm gold particle to the amino-terminus of myosin 5a we are able to measure the movement at sampling rates up to 1000 Hz and follow the movement of the unattached labeled myosin head. Using superresolution methods, we have been able to resolve the single stepping behavior of this myosin into 8 peaks representing individual steps ranging from 11-17 actin monomers with starting head separations of 11, 13, 15, or 17 actin monomers. If the gold bead is placed on the tail of the myosin 5a HMM, we see that the tail transiently moves forward to a position that is further along the actin filament before relaxing back to its rest position. We have begun to analyze the structure and stepping pattern of myosin-6, a processive myosin which moves in the opposite direction on actin compared to other myosins. EM studies show that the angle between the two heads is more variable than in most myosins and that when bound to actin, the motors can be spaced at 13 actins (preferred) or 11 or 15 actin monomers apart. Optical trapping and EM studies demonstrate that the molecule can sometimes take an "inchworm" like step where the two heads occupy closely spaced binding sites. With the lab of Ad Bax we have used NMR to examine the rigidity of the SAH domain of myosin 6.