FIGURE 1.

Sequences and structures of Tm isoforms. A, alignment of the sequences of sk-Tmα, chicken gizzard sm-Tmα, and sm-Tmβ and three non-muscle isoforms expressed in smooth muscle (3). Accession codes are as follows: sk-Tmα, P04268-1; sm-Tmα, P04268-2; sm-Tmβ, P19352-2; nm-Tm2, P09493-3; nm-Tm5, P06753-2; and nm-Tm4, P67936. Residues implicated in interactions with actin (31) and those forming part of alanine clusters (26, 30) are outlined red and green, respectively. B, fragments whose structures were determined here or previously published are shown above and below a diagram of the Tm molecule, where variable regions are highlighted (light blue). For the published structures, Protein Data Bank accession codes are listed in parentheses and the N- and C-terminal coiled-coil stabilizing elements used are indicated (GCN4, Cys bonds or EB1 and XRCC4 fusion proteins).