Myosin cross bridges in skeletal muscles: "rower" molecular motors.
Different classes of molecular motors, "rowers" and "porters," have been proposed to describe the chemomechanical transduction of energy. Rowers work in large assemblies and spend a large percentage of time detached from their lattice substrate. Porters behave in the opposite way. We calculated the number of myosin II cross bridges (CB) and the probabilities of attached and detached states in a minimal four-state model in slow (soleus) and fast (diaphragm) mouse skeletal muscles. In both muscles, we found that the probability of CB being detached was approximately 98% and the number of working CB was higher than 10(9)/mm(2). We concluded that muscular myosin II motors were classified in the category of rowers. Moreover, attachment time was higher than time stroke and time for ADP release. The duration of the transition from detached to attached states represented the rate-limiting step of the overall attached time. Thus diaphragm and soleus myosins belong to subtype 1 rowers.
Lecarpentier
Y
Y
Service de Physiologie, Université Paris-Sud XI, Hôpital Bicêtre, Assistance Publique-Hôpitaux de Paris, 94275 Le Kremlin-Bicêtre, France. lecarpen@enstay.ensta.fr
Chemla
D
D
Pourny
J C
JC
Blanc
F X
FX
Coirault
C
C
D000818:Animals; D003964:Diaphragm / Q000502:physiology*; D007537:Isometric Contraction / Q000502:physiology; D051379:Mice; D008954:Models, Biological; D020409:Molecular Motor Proteins / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D009218:Myosins / Q000502:physiology*; D013997:Time Factors
D020409:Molecular Motor Proteins; D009218:Myosins