THE INFLUENCE OF PROTEIN-FOLDING ON LATE STAGES OF THE SECRETION OF ALPHA-AMYLASES FROM BACILLUS-SUBTILIS

A derivative of the alpha-amylase from Bacillus licheniformis (AmyL) e ngineered to give an active enzyme with increased net positive charge is secreted by Bacillus subtilis with a yield that is significantly lo wer than that of the native enzyme. Ti;is reduction in yield is the re sult of increased proteolysis during or shortly after translocation th rough the cytoplasmic membrane. When we compared the overall rate of f olding of the engineered derivative (AmyLQS50.5) with that of AmyL it exhibited a greater dependency on Ca2+ ions for in vitro folding. When the concentration of Ca2+ in the growth medium was increased, so too did the relative yield of AmyLQS50.5. We discuss the importance of sec retory protein folding at the membrane/cell mall interface with respec t to the yield of native and heterologous proteins from B. subtilis. ( C) 1998 Federation of European Biochemical Societies.