Contractile proteins tissue specific and developmentally regulated gene expression

7 Contractile proteins tissue specific and developmentally regulated gene expression 

Actin and myosin are the principal contractile proteins of the three different t es of vertebrate muscle skeletal (or striated) muscle, cardiac muscle and smooth (non-striated) muscle. Muscle protein makes up approximately 40% of body protein. Actin comprises about 25% and myosin about 50% of myofibrillar protein. In striated muscles, myosin is the principal protein of the thick filaments, and actin the thin filaments. Shortening of the myofibrils is achieved by sliding the thick and thin filaments to increase the overlap between them (see Rayment Holdea 1994). Many of the other proteins assist in this process (see Harold, 1986). Actin and myosin also occur in non-muscle cells, but their spatial organisation is more variable and less regular and 

Protein Location Subunit size Isoforms Mechanisn of isoform generation Function 

Myosin Thick filament 2MyHC (200 kDa)-l-2MyLCl/3 (20 kDa)-F2MyLC2 (20 kDa) total 500 kDa 5 fast, 3 slow and 2 smooth muscle isoforms 30 genes mainly gene duplication, some alternative splicing Contraction 

Actin Thin filament 42 kDa 6 including 3a, iP and 2y 6-11 genes gene duplication Contraction 

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