Cloning and construction of human βMHC cDNA expression plasmids. (A) The three overlapping cDNA clones (λcDNA4, 13, and 10) used for construction of the 6-kbp, fulllength human βMHC cDNA are shown below the representation of the full-length cDNA (βMHC cDNA). The restriction sites SmaI (S), BamHI (B), and AatII (A) were used to assemble the full-length clone. Subclones KS5′, c13-5′, and c13-M were used to insert the epitope tag sequences or for generation of the mutant codons. Also listed are the full-length, epitope tagged clones used. (B) Single letter amino acid sequence of wild-type myosin from several species are compared. The numbering is based upon the published human βMHC sequence (Liew et al., 1990). The underlined area is involved in ATP binding. 1, human βMHC; 2, chick sarcomeric MHC (Molina et al., 1987); 3, rat embryonal sarcomeric MHC (Strehler et al., 1986); 4, Ceanorhabditis elegans MHC A (Karn et al., 1983); 5, chick smooth muscle MHC (Yanagisawa et al., 1987); 6, Dictyostelium discoideum (Warrick et al., 1986); 7, Acathamoeba castellanii myosin II (Hammer et al., 1987).