SYNEMIN CONTAINS THE ROD DOMAIN OF INTERMEDIATE FILAMENTS

We have screened a lambda gt11 cDNA library from chicken gizzard muscl e with polyclonal antiserum to avian synemin. Immunopositive clones we re characterized and sequenced. Computer searches identified primarily intermediate filament (IF) proteins as being homologous to the synemi n clones. Synemin's sequence contained all structural features charact eristic of the rod domain of IF proteins: (a) its length (approximatel y 310 amino acids), (b) the heptad repeat pattern of hydrophobic resid ues of coiled-coil proteins, (c) subdomain structure of the IF rod, by which helical subdomains (1A, 1B, 2A, and 2B) are separated by three short non-helical Linker regions, and (d) several potential intrahelic al ion pairs along the sequence. We also confirmed the presence of the IF rod domain at the protein level by immunoblotting a proteolytic di gest of synemin by using a monoclonal antibody specific to the rod dom ain of IFs. (C) 1995 Academic Press, Inc.