Provides a biochemical mechanism for myosin ATPase inhibition by magnesium through a chelate complex involving SH(1) and SH(2) sites, which is disrupted by actin.
May inform myosin-targeted cardiac therapies; leaves open translation from animal biochemistry to clinical practice.
It is suggested that under physiological conditions (> 1 mM Mg(2+)) MgATP binds to myosin to form a chelate involving the two reactive sulfhydryl sites (SH(1) and SH(2)). The stability of the chelate structure results in marked inhibition of the myosin ATPase in the presence of millimolar magnesium ion. The inhibitory effect of magnesium ion can be eliminated chemically by blocking either the SH(1) or SH(2) site since this precludes formation of the chelate. In muscle, actin apparently behaves in a similar fashion in that its interaction with myosin causes a disruption of the chelate structure.
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Burke et al. (1973) studied this question.
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