EFFECT OF SIGNAL PEPTIDE ALTERATIONS AND REPLACEMENT ON EXPORT OF XYLANASE-A IN STREPTOMYCES-LIVIDANS

Starting from its translation initiation site, the Streptomyces livida ns xylanase A signal peptide consists of 41 amino acids, This signal p eptide was deleted and successively replaced with one of six signal pe ptides from other enzymes secreted by S. lividans and by a signal pept ide from the outer membrane protein (LamB) of Escherichia coli. Deleti on of the xylanase A signal peptide or modification of its cleavage si te abolished secretion of the enzyme, Replacement with the signal pept ides of either xylanase B, cellulase A, mannanase, or acetylxylan este rase produced equivalent amounts of xylanase A, while the signal pepti des of cellulase B, xylanase C, and LamB secreted less enzyme than did the wild type, All the clones exhibited the same transcription levels , which indicated that the variations in xylanase production were due to the natures of the signal sequences.