Chemical and immunological study of colicins e(1), k, a, and q.

Colicins are proteins and, regardless of their origin, can exist in one of two forms, free or bound. When bound, the other constituent is a polysaccharide, but the ratio of the bound form to the free form is dependent on whether the colicin is extracted from an induced or a noninduced strain. Even after extensive purification, traces of polysaccharides persist, and this may be responsible for the partial resistance of colicins to denaturation. The different colicins examined showed differences in their electrophoretic mobility as well as in their amino acid content. However, similarities do exist as has been shown by the demonstration of a common antigen site "L" to colicins E(1), Q, and H.