Conformation of colicin A: apparent difference between cytoplasmic and extracellular polypeptide chain.

Cytoplasmic colicin A has the ability to bind to membranes and to form stable dimers. This form remains stable even in the presence of 1% SDS at 25 degrees C. Both of these properties were not observed for extracellular colicin A suggesting a possible difference in the conformation between cytoplasmic and extracellular colicin A.