PURIFICATION AND SELF-ASSOCIATION EQUILIBRIA OF THE LYSIS-LYSOGENY SWITCH PROTEINS OF COLIPHAGE-186

The CI repressor protein, responsible for maintenance of the lysogenic state, and the Apl protein, required for efficient prophage induction , are the two control proteins of the lysis-lysogeny transcriptional s witch of coliphage 186. These proteins have been overexpressed, purifi ed, and their self-association behavior examined by sedimentation equi librium. Phage 186 CI dimers self-associate in solution through tetram ers to octamers in a concerted process. The Apl protein of 186 is an u nusual example of a helix-turn-helix protein which is monomeric in sol ution.