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Proc Natl Acad Sci U S A. 1998 Jun 9;95(12):6653-8.

Functional transitions in myosin: formation of a critical salt-bridge and transmission of effect to the sensitive tryptophan.

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Department of Structural Analysis, National Cardiovascular Center Research Institute, Fujishiro-dai, Suita, Osaka 565-8565, Japan.


For analyzing the mechanism of energy transduction in the "motor" protein, myosin, it is opportune both to model the structural change in the hydrolytic transition, ATP (myosin-bound) + H2O --> ADP.Pi (myosin-bound) and to check the plausibility of the model by appropriate site-directed mutations in the functional system. Here, we made a series of mutations to investigate the role of the salt-bridge between Glu-470 and Arg-247 (of chicken smooth muscle myosin) that has been inferred from crystallography to be a central feature of the transition [Fisher, A. J., Smith, C. A., Thoden, J. B. , Smith, R., Sutoh, K., Holden, H. M., & Rayment, I. (1995) Biochemistry 34, 8960-8972]. Our results suggest that whether in the normal, or in the inverted, direction an intact salt-bridge is necessary for ATP hydrolysis, but when the salt-bridge is in the inverted direction it does not support actin activation. Normally, fluorescence changes result from adding nucleotides to myosin; these signals are reported by Trp-512 (of chicken smooth muscle myosin). Our results also suggest that structural impairments in the 470-247 region interfere with the transmission of these signals to the responsive Trp.

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