Filamentous smooth muscle myosin is regulated by phosphorylation

Journal Article · Fri Dec 01 04:00:00 EST 1989 · Journal of Cell Biology; (USA)

DOI:https://doi.org/10.1083/jcb.109.6.2887· OSTI ID:5037652

Trybus, K M ^[1]

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1. Brandeis Univ., Waltham, MA (USA)

The enzymatic activity of filamentous dephosphorylated smooth muscle myosin has been difficult to determine because the polymer disassembles to the folded conformation in the presence of MgATP. Monoclonal antirod antibodies were used here to fix dephosphorylated myosin in the filamentous state. The steady-state actin-activated ATPase of phosphorylated filaments was 30-100-fold higher than that of antibody-stabilized dephosphorylated filaments, suggesting that phosphorylation can activate ATPase activity independent of changes in assembly. The degree of regulation may exceed 100-fold, because steady-state measurements slightly overestimate the rate of product release from dephosphorylated filaments. Single-turnover experiments in the absence of actin showed that although dephosphorylated folded myosin released products at the low rate of 0.0005 s-1. The addition of actin did not increase this rate to any appreciable extent. Dephosphorylated filaments and dephosphorylated heavy meromyosin thus have similar low rates of phosphate release both in the presence and absence of actin. These results show that light chain phosphorylation alone, without invoking other mechanisms, is an effective switch for regulating the activity of smooth muscle myosin filaments.

• OSTI ID: 5037652
• Journal Information: Journal of Cell Biology; (USA), Journal Name: Journal of Cell Biology; (USA) Vol. 109; ISSN 0021-9525; ISSN JCLBA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ACID ANHYDRASES
ANIMALS
ANTIBODIES
ATP-ASE
BIRDS
CHEMICAL REACTIONS
ELECTRON MICROSCOPY
ENZYME ACTIVITY
ENZYMES
FOWL
GLOBULINS
HYDROLASES
ISOTOPE APPLICATIONS
ISOTOPES
MICROSCOPY
MONOCLONAL ANTIBODIES
MUSCLES
MYOSIN
ORGANIC COMPOUNDS
PHOSPHOHYDROLASES
PHOSPHORUS ISOTOPES
PHOSPHORYLATION
PROTEINS
TRACER TECHNIQUES
VERTEBRATES