Molecular mechanics of mouse cardiac myosin isoforms

Am J Physiol Heart Circ Physiol. 2002 Oct;283(4):H1446-54. doi: 10.1152/ajpheart.00274.2002.


Two myosin isoforms are expressed in myocardium, alphaalpha-homodimers (V(1)) and betabeta-homodimers (V(3)). V(1) exhibits higher velocities and myofibrillar ATPase activities compared with V(3). We also observed this for cardiac myosin from normal (V(1)) and propylthiouracil-treated (V(3)) mice. Actin velocity in a motility assay (V(actin)) over V(1) myosin was twice that of V(3) as was the myofibrillar ATPase. Myosin's average force (F(avg)) was similar for V(1) and V(3). Comparing V(actin) and F(avg) across species for both V(1) and V(3), our laboratory showed previously (VanBuren P, Harris DE, Alpert NR, and Warshaw DM. Circ Res 77: 439-444, 1995) that mouse V(1) has greater V(actin) and F(avg) compared with rabbit V(1). Mouse V(3) V(actin) was twice that of rabbit V(actin). To understand myosin's molecular structure and function, we compared alpha- and beta-cardiac myosin sequences from rodents and rabbits. The rabbit alpha- and beta-cardiac myosin differed by eight and four amino acids, respectively, compared with rodents. These residues are localized to both the motor domain and the rod. These differences in sequence and mechanical performance may be an evolutionary attempt to match a myosin's mechanical behavior to the heart's power requirements.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Actins / metabolism
  • Adenosine Triphosphatases / metabolism
  • Amino Acid Sequence
  • Animals
  • Cardiac Myosins / chemistry*
  • Cardiac Myosins / metabolism*
  • Female
  • Isomerism
  • Male
  • Mice
  • Molecular Motor Proteins / chemistry
  • Molecular Motor Proteins / metabolism
  • Myocardial Contraction / physiology
  • Myocardium / metabolism*
  • Myofibrils / enzymology
  • Myosin Subfragments / chemistry
  • Myosin Subfragments / metabolism
  • Protein Structure, Tertiary
  • Smooth Muscle Myosins / chemistry
  • Smooth Muscle Myosins / metabolism
  • Ventricular Myosins / chemistry
  • Ventricular Myosins / metabolism


  • Actins
  • Molecular Motor Proteins
  • Myosin Subfragments
  • Adenosine Triphosphatases
  • Cardiac Myosins
  • Smooth Muscle Myosins
  • Ventricular Myosins