ABSTRACT
Signal sequences are N-terminal extensions o f newly synthesized secretory and membrane proteins. They are usually 16 to 30 am ino acid residues in length and comprised o f a hydrophilic, usually positively charged N-terminal region, a central hydrophobic dom ain and a C-term inal region with the cleavage site for signal peptidase. Besides these com m on character istics, signal sequences do not share sequence similarity and some are more than 50 am ino acid residues long.
