EFFECT OF ALTERATION OF CHARGED RESIDUES AT THE N-TERMINI OF SIGNAL PEPTIDES ON PROTEIN EXPORT IN BACILLUS-SUBTILIS

The role of positively charged residues at the N termini of signal pep tides in protein export has been studied in Bacillus subtilis. Bacillu s signal peptides (alkaline protease [Apr] and neutral protease [Npr] from Bacillus amyloliquefaciens) were altered and fused to mature leva nsucrase (Lvs). The effects of the various alterations on the export o f Lvs in B. subtilis were determined. The replacement of positively ch arged residues with neutral residues in both Apr and Npr signal peptid es resulted in a slight defect in the export of Lvs from B. subtilis. Introduction of a negatively charged residue (aspartic acid) at the N terminus of Npr signal peptide blocked the export of Lvs. However, Apr signal peptide with a net charge of -3 (three aspartic acid residues) was still functional.