Demonstration of a precursor-product relationship between soluble and cross-linked elastin, and the biosynthesis of the desmosines in vitro.
Direct evidence showing that a soluble form of elastin is the precursor of cross-linked elastin was obtained from pulse-chase experiments using chick embryo aortas and by demonstrating the conversion of soluble elastin into cross-linked elastin in a cell-free system. Acetic acid extracts of embryonic chick aorta pulse-labeled with [14C]lysine contain two radioactive proteins of molecular weights 74,000 and 138,000 which have been identified previously as soluble elastin and the pro-alpha chain of collagen, respectively. In pulse-chase experiments, the radioactivity incorporated in the soluble elastin during the pulse with [14C]lysine disappeared during a 24-hour chase with [12C]lysine and 89% of that which disappeared was accounted for in the desmosines of alkali-insoluble elastin. The disappearance of the radioactivity from the soluble fraction and its appearance in the desmosines of elastin were inhibited by beta-aminopropionitrile, a specific inhibitor of the cross-linking enzyme lysyl oxidase. In addition in vitro experiments, it was shown that the radioactivity in the desmosines of elastin can arise from that present in an acid-soluble precursor protein. This precursor protein is soluble elastin, as demonstrated by the formation of desmosines when a homogeneous preparation of soluble elastin was incubated with purified lysyl oxidase.
D000596:Amino Acids / Q000096:biosynthesis*; D000818:Animals; D001011:Aorta / Q000378:metabolism*; D002642:Chick Embryo; D002645:Chickens; D003895:Desmosine / Q000096:biosynthesis*; D004549:Elastin / Q000096:biosynthesis* / Q000302:isolation & purification; D008970:Molecular Weight; D011498:Protein Precursors / Q000096:biosynthesis*; D008249:Protein-Lysine 6-Oxidase / Q000378:metabolism; D013552:Swine; D013997:Time Factors
D000596:Amino Acids; D011498:Protein Precursors; D003895:Desmosine; D004549:Elastin; D008249:Protein-Lysine 6-Oxidase