Structural Analysis of Myosin Genes Using Recombinant DNA Techniques2

Myosin, the major protein of the myofibril, consists of two heavy chains with a molecular weight (MW) of 200,000, complexed with four light chains of MW 17,000 to 21,000. Both the heavy and light chains exhibit polymorphisms that are tissue-specific and developmental stage-specific. Myosin heavy chains and light chains appear to be represented in the genome as multigene families in various species, including chickens, cattle, humans, rats, rabbits and nematodes. Myosin heavy-chain proteins have a high amino acid sequence homology among isoforms, and the genes for each isoform likewise exhibit a high degree of nucleotide sequence conservation. The myosin heavy-chain genes have a complex structure and contain up to 65% intervening sequence composed of up to 20 or more individual introns. Partial sequence data, transcriptional orientation and tissue of expression have been determined for several myosin heavy-chain genes. The use of recombinant DNA and associated techniques will eventually yield definitive information on the control of expression of each individual gene, as well as factors that regulate expression of closely related isoforms.