Identification of the primary translation product of elastic mRNA

Poly (A) RNA was prepared from matrix free cells derived from the major thoracic arteries of 17-day old chick embryos. This was translated in a messenger-dependent reticulocyte cell-free system in the presence of [35S]-methionine, [3H]-proline or [3H]-valine. The translation products were analyzed by SDS polyacrylamide gel electrophoresis and fluorography and elastin-related products were immunoprecipitated by the addition of anti-elastin sheep antiserum in the presence of proteinase inhibitors and the precipitate analyzed by the same technique. The elastin-related products were found to consist of a doublet of two closely related polypeptides (mol. wts. 70,000 and 73,000) comigrating with a tropoelastin standard. Unhydroxylated pro alpha 1 and pro alpha 2 collagen polypeptides were also found, but no elastin related product corresponding to proelastin. It is concluded that the primary translation product of elastin mRNA consists of two polypeptides between 70,000 and 73,000 mol wt. which are closely related in size and immunoreactivity to tropoelastin.