Molecular mechanics of mouse cardiac myosin isoforms.
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.
Alpert
Norman R
NR
Department of Molecular Physiology and Biophysics, University of Vermont College of Medicine, Burlington 05405, USA.
Brosseau
Christine
C
Federico
Andrea
A
Krenz
Maike
M
Robbins
Jeffrey
J
Warshaw
David M
DM
D000199:Actins / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D024722:Cardiac Myosins / Q000737:chemistry* / Q000378:metabolism*; D005260:Female; D007536:Isomerism; D008297:Male; D051379:Mice; D020409:Molecular Motor Proteins / Q000737:chemistry / Q000378:metabolism; D009200:Myocardial Contraction / Q000502:physiology; D009206:Myocardium / Q000378:metabolism*; D009210:Myofibrils / Q000201:enzymology; D015879:Myosin Subfragments / Q000737:chemistry / Q000378:metabolism; D017434:Protein Structure, Tertiary; D024745:Smooth Muscle Myosins / Q000737:chemistry / Q000378:metabolism; D024723:Ventricular Myosins / Q000737:chemistry / Q000378:metabolism
D000199:Actins; D020409:Molecular Motor Proteins; D015879:Myosin Subfragments; D000251:Adenosine Triphosphatases; D024722:Cardiac Myosins; D024745:Smooth Muscle Myosins; D024723:Ventricular Myosins