In vitro translation of elastin mRNA and processing of the translated products and the signal sequence of elastin a

Abstract

Chick embryo aorta mRNAs were translated in a gel-filtered reticulocyte lysate. The translated products showed two elastin-related proteins (a and b; relative mass ~ 70 000). The translated elastin a protein was separated essentially free of the b protein by centrifugation and sodium dodecyl sulfate (SDS) – polyacrylamide gel electrophoresis. The a protein was then electroeluted from the SDS–polyacrylamide gel and a partial sequence was determined by automated Edman degradation. The NH2-terminal presequence of the elastin a protein is[Formula: see text]The assigned sequence is identical to that reported for the b protein. Translation of chick embryo aorta mRNA in the presence of dog pancreas microsomal membranes segregated the a and b proteins into membrane vesicles and cotranslationally cleaved their respective presequences. The processed a and b elastin proteins were isolated together and NH2-terminal proline positions were determined. These are[Formula: see text]These proline positions 4 and 8 are identical to those for NH2-terminal sequence for tropoelastin. This suggests that the signal peptidase removes the 24-residue signal peptide and thus directly generates the tropoelastin sequence, with no NH2-terminal prosequence as the intermediate.