EFFECT OF CHICKEN LYSOZYME SIGNAL PEPTIDE ALTERATIONS ON SECRETION OFHUMAN LYSOZYME IN SACCHAROMYCES-CEREVISIAE

To investigate the structural requirements and functions of the N-term inal and the C-terminal regions of the chicken lysozyme signal peptide , the amino acids of each region were altered. The replacement of Gly( -1) and Leu(-2) with Pro(-1) and Ala(-2) or Val(-2), respectively, res ulted in the complete shift of the cleavage site from position -1 to - 2 in yeast (Saccharomyces cerevisiae). This shows that the introductio n of a turn-promoting residue like Pro makes it possible to control th e cleavage site of the signal peptide. Deletion of the positive charge and introduction of a negative charge in the N-terminal region decrea sed the lytic activity of secreted human lysozyme (HLY) and processing efficiency of preHLY, but the length and additional positive charge i n this region had little influence. This suggests that the length of t he N-terminal region scarcely influences the function of the signal pe ptide and that this region possibly interacts with the endoplasmic ret iculum membrane to initiate the translocation of preprotein, similar t o prokaryotic signal peptide. However, it needs only minimum positive charge for its function.