Abstract: The invention relates to a protein stabilizing sequence particularly useful for stabilization of proteolytically sensitive proteins. The sequence includes a relatively small number of amino acids that may be expressed fused with a proteolytically sensitive protein. The most effective stabilization sequences assume .alpha.-helix structures with a hydrophobic face and a positively charged polar face which appear to require proper orientation with respect to each other. Other aspects of the invention include cloning vectors incorporating a gene sequence encoding the stabilization polypeptide and production of stabilized antigenic proteins.