Elastin

Literature References: Elastic, load-bearing protein fibers of animal connective tissue, particularly the ligaments of the vertebrae and the walls of the large arteries. Elastin is an insoluble, highly cross-linked hydrophobic protein, rich in nonpolar amino acid residues, such as valine, leucine, isoleucine, and phenylalanine. On the average, about every third residue is glycine and about every ninth residue is a prolyl residue. Unlike collagen, q.v., which is rich in hydroxyproline, elastin contains only modest amounts. At least two types of elastin are distinguishable: type I elastin isolated from liga-mentum nuchae, aorta or skin and type II elastin isolated from cartilage. The most ready source of high purity elastin is the ligamentum nuchae of the larger ruminants: Partridge et al., Biochem. J. 61, 11 (1955). Amino acid composition studies: Petruska, Sandberg, Biochem. Biophys. Res. Commun. 33, 222 (1968). Its elastic properties are brought about by a cross-linked structure. Identification of new cross-linking amino acids in elastin: Partridge et al., Biochem. J. 93, 30C (1964); Franzblau et al., Biochem. Biophys. Res. Commun. 21, 575 (1965); Starcher et al., Biochemistry 6, 2425 (1967). Molecular model: Gray et al., Nature 246, 461 (1973). Review: Partridge, Adv. Protein Chem. 17, 227-302 (1962); C. Franzblau, "Elastin" in Comprehensive Biochemistry vol. 26c, M. Florkin, E. H. Stotz, Eds. (Elsevier, New York, 1971) pp 659-712; Ross, Bornstein, Sci. Am. 224, 44 (June, 1971). Book (in English): I. Banga, Structure and Function of Elastin and Collagen (Akademiai Kiado, Budapest, 1967). Series of articles on structure, biosynthesis, and immunology: Methods Enzymol. 82, 559-765 (1982).

Properties: Purified elastin has a pale yellow color and a bluish fluorescence in uv light. Resists acid and alkaline hydrolysis. Practically insol in a wide range of hydrogen-bond-breaking solvents at temps up to 100° and swells, but does not dissolve, in phenolic solvents. It appears practically impossible to bring elastin into soln except by hydrolytic reagents capable of rupturing peptide bonds. Elastin is one of only a few polymeric substances which, in the presence of water, exist in a form with rubber-like extensibility and low modulus of elasticity. Enzymes which dissolve fibers of the insol protein elastin undamaged and free from contamination are called elastases.