Expression in Escherichia coli and a functional study of a beta-troponin T 25 kDa fragment of rabbit skeletal muscle.

A 25 kDa fragment of beta-type troponin T (beta-TnT) was expressed in Escherichia coli, and its function as a component of the regulatory system for actomyosin ATPase was compared with that of the authentic counterpart, the full length alpha-TnT. The expressed species, designated as beta-TnT(N'-208), consists of 208 residues. It lacks the entire variable region at the amino-terminus and, near the carboxyl-terminus, a segment of 14 residues is changed from the alpha-type to the beta-type sequence. Functional tests indicated that the truncated beta-TnT was not distinguishable from the full length alpha-TnT, suggesting that neither deletion of the variable N-terminal region nor alteration of the type has a significant effect on the regulatory action of TnT.