NATIVE AND HETEROLOGOUS PROTEIN SECRETION BY STREPTOMYCES-LIVIDANS

The secretion of the heterologous parathion phosphotriesterase in S. l ividans using the Streptomyces beta-galactosidase signal sequence was further characterised using a pulse/chase system, Unsecreted cell-asso ciated protein in both the precursor and signal-cleaved forms was obse rved when the protein was expressed from both low- and high-copy vecto rs, Fractionation of the cells followed by immunoprecipitation with ph osphotriesterase antibody suggests that the precursor is membrane-boun d while the signal cleaved form is present in the soluble fraction, Pr eliminary data on the processing of alpha-amylase, a native Streptomyc es protein, showed much more rapid processing and secretion, but never theless still revealed cell-associated, signal-cleaved protein.