Chemical composition of isolated rat skeletal sarcolemma

Isolated rat skeletal muscle sarcolemmal tubes contained 78.1% protein, 13.1% lipid and 3.3% neutral carbohydrate. Gas-liquid chromatography of the total sarcolemmal carbohydrates showed the presence of fucose (0.28%), mannose (0.44%), galactose (0.95%), neuraminic acid (0.31%) and larger quantities of glucose (1.58%), glucosamine (2.59%) and galactosamine (2.03%). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed 30 to 35 protein bands including three major bands at 170,000, 140,000 and 44,000 mol wt. Amino acid analysis showed the sarcolemma to contain small amounts of proteins characteristic of collagen and relatively large amounts of acidic amino acids (21.5% glutamic and aspartic acids). Lithium 3,5-diiodo salicylate (LIS) extracted a fraction of the external lamina of the sarcolemma (designated ELS). The ELS was rich in glucuronic acid and hexosamines as well as having an increased proportion of acidic amino acids. The ELS contained no hydroxyproline and had less lipid than whole sarcolemma.