Yount, Ralph G.
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Research Interests
Professor Youmt’s primary interests are in the molecular mechanism of muscle contraction and of motility in biological systems. His group prepares new analogs of ATP to be used as monitors of contractile events and/or as probes of the molecular structure of contractile proteins. Some recent derivatives contain stable free radicals (spin probes) or fluorescent/luminescent probes attached to ATP or ATP-like molecules that also contain photoreactive groups capable of forming covalent bonds to proteins upon irradiation of appropriate complexes. These probes are then covalently bound near the ATP-binding site and have been found not to interfere with contractile events. We “trap” the ADP product of hydrolysis of these ATP-like molecules at the active site of myosin (the major contractile protein in muscle) with transition state analogs of inorganic phosphate, e.g., vanadate or A1F4. Extraneous ADP analog is removed by washing and myosin then photolabeled specifically in a benign manner. Thus it is possible for the first time to introduce EPR or fluorescent/luminescent reporter groups onto the “heads” of myosin in a specific manner even in complex muscle fibers to allow monitoring of movement of the heads during the contractile cycle. Other studies are aimed at using these new derivatives to reveal the nature of force generation by kinesin and kinesin-like molecules that move on tracks of microtubules.

Publications
Chen, S., Grammer, J., Cooke, R., Pate, E., Yount, R. G. Synthesis and characterization of novel spin-labeled photoaffinity nonnucleoside analogues of ATP as structural and EPR probes for myosn. Bioconjug Chem 2000 5:725-733.

Wang, D., Luo, Y., Cooke, R., Grammer, J., Pate, E., Yount, R.G. Synthesis of a spin-labeled photoaffinity ATP analogue, and its use to specifically photolabel myosin cross-bridges in skeletal muscle fibers. J. Muscle Res Cell Motil (1999) 8:743-753.

Gulick, A.M., Bauer, C.B., Thoden, J.B., Pate, E., Yount, R.G., Rayment, I. X-ray structures of the Dictyostelium discoideum myosin motor domain with six non-nucleotide analogs. J. Biol. Chem (2000) 275:398-408.

Chen, X., Siems, W.F., Asbury, G.R., Yount, R.G. Fingerprint patterns from laser-induced azido photochemistry of spin-labeled photoaffinity ATP analogs in matrix-assisted laser desorption/ionization mass spectrometry. J. Am Soc Mass Spectrom (1999) 12:1337-1340.

Xiao, M., Li, H., Snyder, G.E., Cooke, R., Yount, R.G. Selvin, P.R. Conformational changes between the active-site and regulatory light chain of myosin as determined by luminescence resonance energy transfer: the effect of nucleotides and actin. Proc Natl Acad Sci USA (1998) 26:15309-15314.

Deng, H., Wang, J., Callender, R.H. Grammer J.C. Yount, R.G. Raman difference spectroscopic studies of the myosin S1.MgADP. vanadate complex. Biochemistry. (1998) 31:10972-10979.