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The actin‐activated ATPase of regulated and unregulated scallop heavy meromyosin
Author(s) -
Jackson Andrew P.,
Warriner Karen E.,
Wells Christine,
Bagshaw Clive R.
Publication year - 1986
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(86)80317-9
Subject(s) - heavy meromyosin , scallop , atpase , myosin , actin , centrifugation , chemistry , biochemistry , biophysics , myosin atpase , biology , enzyme , fishery
Single‐turnover kinetic analysis indicates that scallop heavy meromyosin (HMM) preparations contain a small fraction of unregulated molecules which dominate the steady‐state ATPase activity in the absence of Ca 2+ . This fraction was removed by rapid centrifugation during an effective single turnover of the ATPase in the presence of actin. The maximum ATPase activity of a scallop myosin head was estimated as 10 s −1 by cross‐linking subfragment 1 to F‐actin. HMM became Ca 2+ ‐insensitive during the cross‐linking procedure. Attachment of spectroscopic probes to the reactive thiol group of scallop HMM resulted in the retention of ATPase activity but a loss in Ca 2+ sensitivity.