Biosynthesis of Tropoelastin by Elastic Cartilage

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Abstract
Elastic ear cartilage and aortae from nine-day-old hamsters were incubated in Krebs-Ringer medium containing ascor-bate, β-aminopropionitrile and either [14C]proline or [3H] valine. The [14C] proline-labeled proteins were separated by chromatography on Agarose A-5 m in sodium dodecyl sulfate and their [14C]-hydroxyproline content measured. A fraction having an approximate molecular weight of 70,000 measured by polyacrylamide gel electrophoresis had a [14C] hydroxyproline content of 9.1% in the cartilage and 11.8% in the aorta. This fraction was also relatively heavily labeled with [3H]valine. The 70,000 dalton, [3H]valine-labeled protein of both the aorta and ear cartilage was precipitated by elastin-specific antibody prepared against hamster insoluble aorta elastin, but no higher molecular weight protein was immunoprecipitated. Based on these results we identify the 70,000 dalton protein from the elastic cartilage as tropoelastin.