Determination of methylated basic amino acids, 5-hydroxylysine, and elastin crosslinks in proteins and tissues

Myosin, actin, collagen, and elastin of adult bovine diaphragm and porcine and avian skeletal muscle tissues and their separated intracellular and extracellular muscle protein fractions have been determined by chromatographic methods developed to quanti tate their unique basic amino acids. In this direct chemical approach the determination of the myofibrillar myosin and actin content of skeletal muscle is based on the amounts of Nτ-methylhistidine present, and collagen from the amount of 5-hydroxylysine present. Elastin was also determined from the amounts of desmosine found. Skeletal muscles were found to contain between 10.2–11.5% actin and 21.3 to 24.0% myosin, corresponding to 21.1% and 44.0% of the myofibrillar proteins (52.3% of the total muscle proteins), between 37.6–46.3% other SDS-soluble intracellular proteins, and 4.7 to 10.2% SDS-insoluble extracellular matrix muscle proteins. Total skeletal muscle collagan ranged from 2.8 to 5.9%, while elastin accounted for an estimated 0.063–0.143%, and the transcellular matrix SDS-insoluble proteins accounted for the remaining 1.8%.