TY - JOUR
T1 - The myosin head can bind two actin monomers
AU - Andreev, O. A.
AU - Borejdo, J.
N1 - Funding Information:
Baylor Research Foundation Baylor University Medical Center 3812 Elm St., Dallas, TX 75226
PY - 1991/5/31
Y1 - 1991/5/31
N2 - Force impulse is thought to be generated in muscle when myosin head (S-1), while weakly bound to actin filament, undergoes orientational change to form a strong (rigor) bond with actin. There is ample evidence that this bond involves interaction of 1 myosin head with 1 actin monomer. However, X-ray diffraction data of muscle decorated with S-1, as well as recently proposed model of the thin filaments, suggested that each S-1 molecule interacted with two actin monomers. We reinvestigated this controversy and found that the stoichiometry of acto-S-1 bond depended on the relative amounts of actin and myosin present during titrations: when increasing amounts of actin were added to a fixed amount of S-1 (i.e. when myosin heads were initially in excess over actin), the saturating stoichiometry was 1 mol of S-1 per 1 mol of actin. However, when increasing amounts of S-1 were added slowly to a fixed amount of F-actin (i.e. when actin was initially in excess over S-1), the stoichiometry at saturation was 1 mol of S-1 per 2 mols of actin. The ability of S-1 to bind either one or two actin monomers suggests a way that force could be generated during muscle contraction.
AB - Force impulse is thought to be generated in muscle when myosin head (S-1), while weakly bound to actin filament, undergoes orientational change to form a strong (rigor) bond with actin. There is ample evidence that this bond involves interaction of 1 myosin head with 1 actin monomer. However, X-ray diffraction data of muscle decorated with S-1, as well as recently proposed model of the thin filaments, suggested that each S-1 molecule interacted with two actin monomers. We reinvestigated this controversy and found that the stoichiometry of acto-S-1 bond depended on the relative amounts of actin and myosin present during titrations: when increasing amounts of actin were added to a fixed amount of S-1 (i.e. when myosin heads were initially in excess over actin), the saturating stoichiometry was 1 mol of S-1 per 1 mol of actin. However, when increasing amounts of S-1 were added slowly to a fixed amount of F-actin (i.e. when actin was initially in excess over S-1), the stoichiometry at saturation was 1 mol of S-1 per 2 mols of actin. The ability of S-1 to bind either one or two actin monomers suggests a way that force could be generated during muscle contraction.
UR - http://www.scopus.com/inward/record.url?scp=0025866119&partnerID=8YFLogxK
U2 - 10.1016/0006-291X(91)91990-T
DO - 10.1016/0006-291X(91)91990-T
M3 - Article
C2 - 2043120
AN - SCOPUS:0025866119
SN - 0006-291X
VL - 177
SP - 350
EP - 356
JO - Biochemical and Biophysical Research Communications
JF - Biochemical and Biophysical Research Communications
IS - 1
ER -