A survey of interactions made by the giant protein titin.

A simple solid-phase binding assay was used to screen for interactions that the giant myofibrillar protein titin makes with other sarcomeric proteins. The titin used in the tests was purified by a modified procedure that results in isolation of approximately 20 mg relatively undegraded protein in < 24 h. In addition to the approximately 3 MDa polypeptide, bands at approximately 160 kDa and approximately 100 kDa were also consistently seen on gels. Binding of titin to myosin, C-protein, X-protein and AMP-deaminase was observed. The interaction with myosin appears to be with the light meromyosin part of the molecule.