Key result
MLCK and PKA phosphorylation both increased cross-bridge proximity to actin, but only MLCK reduced interfilament spacing by 2 nm (3.5%), explaining its unique effect on Ca(2+) sensitivity.
RLC and cMyBP-C phosphorylation modulate the kinetics of cardiac force development by increasing cross-bridge proximity to actin, but only RLC phosphorylation affects lattice spacing to increase Ca2+ sensitivity.
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MLCK-specific lattice effects extend sarcomere regulation mechanisms; leaves open human HF relevance.
Colson et al. (2010) studied cardiac force development. MLCK treatment vs. PKA treatment was evaluated on equatorial intensity ratios (I(1,1)/I(1,0)) and lattice spacings (d(1,0)). MLCK and PKA phosphorylation both increased cross-bridge proximity to actin, but only MLCK reduced interfilament spacing by 2 nm (3.5%), explaining its unique effect on Ca(2+) sensitivity.
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