Myosin-binding protein which plays a role in cardiac function (PubMed:28778945). Seems to regulate conduction in the atria and ventricular conduction systems (PubMed:28778945). Expressed in the atria as well as in discrete puncta throughout the right ventricular wall and septum. Knockout mouse hearts exhibit a 36% reduction in fractional shortening and an increased diastolic ventricular chamber size (PubMed:28778945). Mutants show cardiac conduction system abnormalities with aberrant atrioventricular conduction and an increased rate of arrhythmia (PubMed:28778945). Belongs to the immunoglobulin superfamily. MyBP family.