James A. Spudich
Web: No lab page.
Our general research interest is the molecular basis of cell motility and muscle contraction. We have two primary research interests, the molecular basis of energy transduction that leads to ATP-driven myosin movement on actin, and the molecular basis of cytokinesis, including the spatial and temporal control of assembly of the actin-myosin based contractile ring.
We work on two experimental systems: mammalian muscle and Dictyostelium. Each of these systems has its special advantages. Skeletal muscle has the most highly organized contractile apparatus of any cell type, and the chemistry and biochemistry of muscle actin and myosin are most advanced.
Dictyostelium, the cell that commands most of our attention, exhibits all of the behavior of nonmuscle mammalian cells, and, unlike other eukaryotic cells, can be grown in large amounts for biochemical work. Furthermore, DNA-mediated transformation is being applied to this organism, and our discovery of high-frequency homologous recombination in this organism has proved to be general.
Our approaches include biochemical and structural studies of actin, myosin, and associated regulatory proteins. In addition, we have designed and developed in vitro assays for ATP-dependent movement of purified myosin on filaments reconstituted from purified actin. These assays allow us to analyze mutant myosin molecules for altered function. The site-directed mutagenized forms of myosin are obtained by gene cloning and expression in Dictyostelium. Our demonstration that the Dictyostelium myosin gene can undergo homologous recombination allows us to also probe the effects of the altered myosin forms on the phenotype of the cell.
Finer, J. T., Simmons, R. M. and Spudich, J. A. (1994) Single myosin molecule mechanics: piconewton forces and nanometre steps. Nature 368, (6467): 113-119. (Medline)
Uyeda, T. Q., Ruppel, K. M. and Spudich, J. A. (1994) Enzymatic activities correlate with chimaeric substitutions at the actin-binding face of myosin. Nature 368, (6471): 567-569. (Medline)
Spudich, J.A., Finer, J., Simmons, B., Ruppel, K., Patterson, and Uyeda, T. (1995). Myosin Structure and Function, Cold Spring Harbor Symposia on Quantitative Biology, Vol 60. Cold Spring Harbor Laboratory Press, pp. 783-791. (Medline)
Moores, S.L., Sabry, J.H., and Spudich, J.A. (1996). Myosin dynamics in live Dictyostelium cells (green fluorescent protein). Proc. Natl. Acad. Sci. USA 93: 443-446. (Medline)
Patterson, B., and Spudich, J.A. (1996). Cold-Sensitive Mutations of Dictyostelium. Myosin Heavy Chain Highlight Functional Domains of the Myosin Motor. Genetics 143: 801-810. (Medline)
Ruppel, K.M., and Spudich, J.A. (1996). Structure-Function of the Myosin Motor Domain: Importance of the 50-kDa Cleft. Mol. Biol. Cell 7: 1123-1136. (Medline)
Simmons, R.M., Finer, J.T., Chu, S., and Spudich, J.A. (1996). Quantitative Measurements of Force and Displacement Using an Optical Trap. Biophys. J. 70: 1813-1822. (Medline)
Uyeda, T.Q.P., Abramson, P.D., and Spudich, J.A. (1996). The neck region of the myosin motor domain acts as a lever arm to generate movement. Proc. Natl. Acad. Sci. USA 93: 4459-4464. (Medline)
