Characterization of the active site of platelet myosin in comparison to smooth and skeletal muscle myosin

Isaac Cohen*, Elizabeth Kaminski, Raphael Lamed, Avraham Oplatka, Andras Mühlrad

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

Heavy meromyosin subfragment-1 from human platelets and chicken gizzard exhibited an identical chromatographic pattern on agarose-ATP columns both in the absence and in the presence of Ca2+ and Mg2+. In the presence of Ca2+, the behavior differed from that of rabbit white skeletal muscle subfragment-1. The reaction of lysyl residues of platelet myosin with 2,4,6-trinitrobenzene sulfonate did not affect the K+- or Mg2+-stimulated ATPase activity. A similar behavior was exhibited by chicken gizzard myosin whereas trinitrophenylation of the more active lysyl residues in skeletal muscle myosin caused a marked increase in Mg2+-stimulated and a decrease in K+-stimulated ATPase activity. These features may point to a similar location of the essential lysyl residue in platelet and smooth muscle myosin, which is different from that of skeletal muscle. Alkylation of thiol groups by N-ethyl maleimide in the absence of added nucleotides resulted in a loss of K+-ATPase and in an increase in the Ca2+-ATPase in all three myosins, the increase for the skeletal myosin being much greater than for the platelet and chicken gizzard preparations. Alkylation of myosin in the presence of MgADP led to a decrease in K+-ATPase of all preparations whereas the Ca2+-ATPase as a function of time exhibited a maximum for the platelet and skeletal muscle proteins. These features may point to a certain similarity with respect to the active site of platelet and smooth muscle myosins and a difference between these and skeletal muscle myosin.

Original languageEnglish
Pages (from-to)249-255
Number of pages7
JournalArchives of Biochemistry and Biophysics
Volume175
Issue number1
DOIs
StatePublished - Jul 1976

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