Autophosphorylation-independent activation of Acanthamoeba myosin I heavy chain kinase by plasma membranes.
Year: 1993
Type: article
Abstract: The three isoforms of Acanthamoeba myosin I (non-filamentous myosin with only a single heavy chain) express actin-activated Mg(2+)-ATPase activity only when phosphorylated at a single site by myosin I heavy chain kinase. The kinase is activated by autophosphorylation that is greatly stimulated by acidic phospholipids. Substantial fractions of the three myosins I and the kinase are associated in situ with membranes, and all four enzymes bind to purified membranes in vitro. We now report that when kinase and myosin I are incubated together with phosphatidylserine vesicles not only does the kinase autophosphorylate more rapidly than soluble kinase in the absence of phosphatidylserine but that, probably as a result, the kinase phosphorylates myosin I more rapidly than soluble kinase phosphorylates soluble myosin I. Similarly, plasma membrane-bound kinase phosphorylates membrane-bound myosin I and activates its actin-activated Mg(2+)-ATPase activity more rapidly than soluble kinase phosphorylates and activates soluble myosin I in the absence of membranes. However, the enhanced activity of membrane-bound kinase (which is comparable to the activity of kinase in the presence of phosphatidylserine) is not due to autophosphorylation of the membrane-bound kinase, which is very much slower than for kinase activated by phosphatidylserine vesicles.
Source: Journal of Biological Chemistry
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: hybrid
Estimated APC paid: $3,430
OpenAlex ID: W1552235801