<P> Skeletal muscle myosin , the most conspicuous of the myosin superfamily due to its abundance in muscle fibers , was the first to be discovered . This protein makes up part of the sarcomere and forms macromolecular filaments composed of multiple myosin subunits . Similar filament - forming myosin proteins were found in cardiac muscle , smooth muscle , and nonmuscle cells . However , beginning in the 1970s , researchers began to discover new myosin genes in simple eukaryotes encoding proteins that acted as monomers and were therefore entitled Class I myosins . These new myosins were collectively termed `` unconventional myosins '' and have been found in many tissues other than muscle . These new superfamily members have been grouped according to phylogenetic relationships derived from a comparison of the amino acid sequences of their head domains , with each class being assigned a Roman numeral ( see phylogenetic tree ) . The unconventional myosins also have divergent tail domains , suggesting unique functions . The now diverse array of myosins likely evolved from an ancestral precursor ( see picture ) . </P>
<P> Skeletal muscle myosin , the most conspicuous of the myosin superfamily due to its abundance in muscle fibers , was the first to be discovered . This protein makes up part of the sarcomere and forms macromolecular filaments composed of multiple myosin subunits . Similar filament - forming myosin proteins were found in cardiac muscle , smooth muscle , and nonmuscle cells . However , beginning in the 1970s , researchers began to discover new myosin genes in simple eukaryotes encoding proteins that acted as monomers and were therefore entitled Class I myosins . These new myosins were collectively termed `` unconventional myosins '' and have been found in many tissues other than muscle . These new superfamily members have been grouped according to phylogenetic relationships derived from a comparison of the amino acid sequences of their head domains , with each class being assigned a Roman numeral ( see phylogenetic tree ) . The unconventional myosins also have divergent tail domains , suggesting unique functions . The now diverse array of myosins likely evolved from an ancestral precursor ( see picture ) . </P>
where is myosin found in the skeletal muscle cells
where is myosin found in the skeletal muscle cells
the sarcomere
the sarcomere