Mechano-chemical Interactions in Cardiac Sarcomere Contraction: A Computational Modeling Study
Fig 2
Schematic representation of Tn activation.
(A) A RU is a functional unit of the sarcomere that is considered to work together. It is composed of 7 actin monomers, one tropomyosin (Tm) molecule, and one troponin complex (Tn). At rest, the C-terminal section of TnI extends over the actin monomer on the adjacent strand reaching to the Tm molecule, hindering its movement [17]. That hindrance is removed upon the conformational changes resulting from Ca2+ binding to that Tn. Note: Tn’s on adjacent actin strands are located in-register with one another, but this is not displayed in the figure. (B) A conformational change in the Tn caused by the binding of calcium to TnC effectively removes the Tm from the blocking position. (C) The thin filament in (A) is viewed from the longitudinal axis. The movement of Tm from the position blocking the XB-binding sites toward the groove reduces the radius (R) from the center of the actin double helix.