Beta-keratin 75-80% of the amino acids in silk, another 10-15% is serine and the final 10% contain bulky side chains such as in tyr, arg, val, asp, and glu. Beta-keratin β-keratin or beta-keratin is a member of a structural protein family found in the epidermis of reptiles and birds . β-keratins were named so because they are components of epidermal stratum corneum rich in stacked β pleated sheets, in contrast to alpha-keratins, intermediate-filament proteins also found in stratum corneum and rich in alpha helices. Because the accurate use of the term "keratin" is limited to the alpha-keratins, the term "beta-keratins" in
Myosin head actin together with the products of ATP hydrolysis, performs a power stroke associated with release of hydrolysis products, and detaches from actin upon binding with new ATP. The detached myosin head then hydrolyses ATP, and performs a recovery stroke to restore its initial position. The strokes have been suggested to result from rotation of the lever arm domain around the converter domain, while the catalytic domain remains rigid. Myosin head Muscle contraction is caused by the sliding action of thick filaments over thin filaments of the myofibril. Myosin is a major component of thick filaments and most myosin molecules are