Regulatory light-chain Cys-55 sites on the two heads of myosin can come within 2Å of each other

Abstract

The di-thiol reagent, 5,5′-dithiobis (2-nitrobenzoic acid) is shown to induce disulfide bond formation between Mercenaria regulatory light-chain Cys-55 sites on either head of scallop hybrid myosin. This indicates that these two sites on opposite heads of myosin can come within 2Å of each other and this confirms a prediction based on earlier data [Chantler, Tao and Stafford (1991) Biophys. J. 59, 1242–1250]. Results demonstrate that myosin heads in solution show a considerable mutual freedom of movement which can be monitored by probes in the vicinity of regulatory light-chain residue 55. Implications for light-chain movement on the myosin head are discussed.