PROTEIN SECRETION IN STREPTOMYCES-GRISEUS N2-3-11 - CHARACTERIZATION OF THE SECA GENE AND ITS GROWTH PHASE-DEPENDENT EXPRESSION

The chromosomal region encoding the secA gene of Streptomyces griseus N2-3-11 was cloned and analyzed. The secA gene encodes a polypeptide o f 939 aa with a molecular mass of 105 kDa. The growth defect of temper ature sensitive Escherichia coli secA mutants was not restored by the S. griseus SecA. The secA promoter was analyzed and the transcriptiona l start point of the gene was determined. Northern blot and Western bl ot analyses revealed a growth phase dependent secA expression. The int egration of an additional copy of the S. griseus secA gene into the ge nome of S. lividans TK23 had no visible effect on the efficiency of pr otein secretion.