Predicted secondary structures of amino‐terminal extension sequences of secreted proteins

Recently it has be en shown that the mRNA for many secreted proteiJ,s translates in cell-free systeJns to yield precursors that are larger than mature proteins. The precursors contain amino-terminal exteJlsions known as signal sequences, of 15-30 residues .of predominantly hydrophobic amino acid residues [I -31. Segregation of the serreted protein into vesicles prepared from pancreatic microso~ml membranes and proteolytic removal of the extensions occur during tr2Jlslation; the compietecf pre protein is not processed [4--7]:Small signal peptides have been detected during processing ES] showing that the sigM protease is endoproteolytic.