Fesselin: a novel synaptopodin-like actin binding protein from muscle tissue

A novel actin binding protein has been isolated from chicken gizzard muscle . When isolated, a pair of proteins with apparent molecular weights of 79 k Da and 103 kDa are obtained; both proteins have a pI near 9.3. Peptide mapp ing indicates that these proteins are related. Antibodies against this prot ein cross-reacted with proteins from other smooth muscle containing tissues as well as skeletal and heart muscle. Traces of cross-reactive material we re also detected in brain and kidney tissue. The affinity of this protein f or actin is ca. 1 x 10(6) M-1. Interestingly, this actin binding protein is a potent actin-bundling agent. A partial sequence analysis confirmed that there were no previously reported homologues in smooth muscle. However, con siderable homology was found with the protein synaptopodin that is found in nervous tissue and kidney but is absent from muscle tissue. It is likely t hat the new protein is a member of the synaptopodin family. We call the smo oth muscle actin binding protein fesselin.