Modeling smooth muscle myosin's two heads: long-lived enzymatic roles and phosphorylation-dependent equilibria.

ABSTRACT: Smooth muscle myosin has two heads, each capable of interacting with actin to generate force and/or motion as it hydrolyzes ATP. These heads are inhibited when their associated regulatory light chain is unphosphorylated (0P), becoming active and hydrolyzing ATP maximally when phosphorylated (2P). Interestingly, with only one of the two regulatory light chains phosphorylated (1P), smooth muscle myosin is active but its ATPase rate is <2P. To explain published 1P single ATP turnover and steady-state ATPase activities, we propose a kinetic model in which 1P myosin exists in an equilibrium between being fully active (2P) and inhibited (0P). Based on the single ATP turnover data, we also propose that each 2P head adopts a hydrolytic role distinct from its partner at any point in time, i.e., one

SUBMITTER: Walcott S 

PROVIDER: S-EPMC2920627 | biostudies-literature | 2010 Aug

REPOSITORIES: biostudies-literature