Studies on the interaction between titin and myosin.

This study examines the interaction of titin and myosin. In order to analyze the domains of myosin contributing to the binding for titin, we conducted a solid phase binding assay. Different portions of myosin (heavy chains, light chains and myosin fragments) were coated on the microtiter wells and reacted with biotinylated titin. Then the binding of biotinylated titin to these polypeptides was detected by using the avidinbiotin-peroxidase method. The results demonstrated that light meromyosin and subfragment 1 were the major domains of myosin interacting with titin. Titin fragments obtained by trypsin digestion were allowed to react with myosin in an affinity column, and the bound fragments were isolated by an acidic elution. Immunoblot analysis of myosin-bound titin fragments revealed that an A-band domain of titin was responsible for the binding of myosin. In addition, biotinylated titin labelled the outer A-bands and Z-bands in intact myofibrils, thus confirming the in situ binding of titin to myosin.