Tropomyosin is a284 residuedimeric coiled-coil protein that interacts in a head-to-tail manner to form linear filaments at low ionic strengths. Polymerization is related to tropomyo-sin’s ability to bind actin, and both properties depend on intact N- and C-termini as well as a-amino acetylation of theN-terminus of the muscle protein. Na-acetylation can be mimicked by an N-terminal Ala-Ser fusion in recombinant tropomyosin (ASTm) produced inEscherichia coli.