The presence of a pyrene label on Cys-374 of actin decreases its affinity for myosin subfragment 1 by less than a factor of 2, and increases the dissociation rate by up to a factor of 2.
A pyrene label attached to Cys-374 of actin has been shown to be a useful probe for monitoring the interaction of actin with myosin subfragments Kouyama & Mihashi (1981) Eur. J. Biochem. 114, 33-38. We report that the presence of this label decreases the affinity of actin for myosin subfragment 1 by less than a factor of 2. The rate of actin binding is unaffected by the label and the dissociation rate is increased by up to a factor of 2. Both the rate of actin binding to, and the rate of actin dissociation from, heavy meromyosin show two phases when monitored by pyrene fluorescence. Thin filiments reconstituted from pyrene-labelled actin show a 5% increase in pyrene fluorescence on binding Ca2+.
Criddle et al. (Sun,) reported a other. Actin labelled with N-(1-pyrenyl)iodoacetamide was evaluated on Affinity and binding/dissociation rates of actin for myosin subfragments. The presence of a pyrene label on Cys-374 of actin decreases its affinity for myosin subfragment 1 by less than a factor of 2, and increases the dissociation rate by up to a factor of 2.
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