New mass spectrometry techniques demonstrate that in vivo phosphorylation patterns of cardiac contractile proteins differ significantly from those identified in vitro, necessitating a reevaluation of their physiological roles.
It is well established that several key proteins of the contractile apparatus are phosphoproteins. This includes myosin binding protein C (MyBP-C), troponin T and troponin I. It is also generally accepted that phosphorylation of these proteins alters their functional properties and that this modulation of function through the action of kinases and phosphatases plays a role in tuning the contractile apparatus to physiological demands. The prime example of this is phosphorylation of troponin I and MyBP-C by PKA as part of inotropic and lusitropic responses to b-adrenergic stimulation.
Marston et al. (2009) studied this question.