Partial characterization of a tropoelastin precursor isolated from chick aorta.

Evidence is presented that indicates tropoelastin is derived from a soluble elastin with a molecular weight of 95000. Tropoelastin and its proposed precursor were isolated from the aortas of copper-deficient chicks. Although it is doubtful that the proposed precursor is an initial product of elastin translation, i.e., a proelastin, it is proposed to be at least a truncated form of proelastin that is converted to tropoelastin. The key to its isolation was the presence of alpha 1-antitrypsin at each step in the purification procedure. The first 11 amino acid residues at the NH2 terminal of the proposed tropoelastin precursor (GGVPGVAVPGGV) are the same as those for tropoelastin. Its amino acid composition is similar to that of tropoelastin, except for higher amounts of acidic amino acid residues. Further, the proposed precursor contains a limited number of aldehydic functions, presumably in the form of peptidyl allysine. This was taken as an indication that the proposed precursor serves as a substract for lysyl oxidase. Under the conditions used for the isolation, the precursor appeared to be in higher concentrations than tropoelastin in aorta extracts from copper-deficient chicks.