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Aorta caldesmon inhibits actin activation of thiophosphorylated heavy meromyosin Mg 2+ ‐ATPase activity by slowing the rate of product release
Author(s) -
Marston Steven
Publication year - 1988
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(88)80245-x
Subject(s) - heavy meromyosin , chemistry , caldesmon , actin , tropomyosin , biophysics , atpase , biochemistry , enzyme , calmodulin , biology
Activation of aorta thiophosphorylated heavy meromyosin (HMM[SP]) Mg 2+ ‐ATPase activity by aorta actin and the fraction of HMM[SP]‐substrate intermediate complexes bound to actin were measured simultaneously. At 25°C the K m for ATPase activation and the dissociation constant for the binding reaction were similar, irrespective of the presence or absence of tropomyosin. Aorta caldesmon (0.1 mol/mol actin) inhibited ATPase activation by 80–90% but did not alter the binding of HMM[SP]‐product intermediates to actin. It is concluded that caldesmon inhibits by slowing the rate‐limiting release of products from the actin‐HMM[SP]·ADP·P i complex.