Characterization of insoluble elastin from copper-deficient pigs. Its usefulness in elastin sequence studies.
Insoluble elastin from copper-deficient animals has an amino acid composition intermediate between mature elastin and salt-soluble elastin (a higher lysine content and correspondingly low number of cross-links relative to the normal protein) and is solubilized by successive treatment with trypsin and chymotrypsin at 4 and 37 degrees C. Small amounts of B3H4 (11 mg--2 g of elastin) reduced allysine, allysine aldol, dehydronorleucine, and dehydromerodesmosine in insoluble elastin from copper-deficient pig aorta. In contrast, desmosine and isodesmosine were reduced only when a large excess of reductant (400 mg borohydride) was included in the reaction mixture. Reduction studies indicated that lysinonorleucine and merodesmosine were present in their dehydro forms to a greater extent in copper-deficient pig elastin than in normal elastin. After reduction with borohydride approximately 35% of the reduced form of the insoluble elastin remained insoluble after digestion with trypsin and chymotrypsin. A peptide containing the aldehyde oxidation product of lysine (allysine) and demonstrating an enrichment in glutamic acid was purified from the reduced form of copper-deficient pig elastin and partially sequenced. Its sequence (Gly-Ala-Glu-allysine-(Glu)...) and amino acid composition suggest: (1) clustering of glutamic acid residues in the elastin molecule, and (2) that allysine residues are not restricted to the alanine-enriched sites described for other elastin cross-links. Insoluble elastin from copper-deficient animals promises to be a useful tool for elastin sequence studies.
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002918:Chymotrypsin; D003300:Copper / Q000172:deficiency*; D004549:Elastin / Q000378:metabolism; D010084:Oxidation-Reduction; D010446:Peptide Fragments / Q000032:analysis; D012995:Solubility; D013552:Swine; D014357:Trypsin
D000596:Amino Acids; D010446:Peptide Fragments; D003300:Copper; D004549:Elastin; D002918:Chymotrypsin; D014357:Trypsin