FLEXIBILITY OF MYOSIN IN PYROPHOSPHATE AND NACL SOLUTIONS : AN ELECTRIC BIREFRINGENCE STUDY

The orientational relaxation time of myosin has been reported as 38 μs when measured in pyrophosphate media at elevated pH (Hvidt et al. 1984) and as 17 μs when measured in 0.3 M KCl at pH 7.3 (Bernengo and Cardinaud 1982). This discrepancy, which is reexamined in the present report, suggests that in KCl solution the rod portion of the myosin molecule is bent with an average angle close to 110°, whereas in pyrophosphate at elevated pH it assumes a nearly straight and rigid conformation