Functional domains of colicin A

Summary A large number of mutations which introduce deletions in colicin A have been constructed. The partially deleted colicin A proteins were purified and their activity in vivo (on sensitive cells) and in vitro (in planar lipid bilayers) was assayed. The receptor‐binding properties of each protein were also analysed. From these results, we suggest that the NH2‐terminal region of colicin A (residues 1 to 172) is involved in the translocation step through the outer membrane. The central region of colicin A (residues 173 to 336) contains the receptor‐binding domain. The COOH‐terminal domain (residues 389 to 592) carries the pore‐forming activity.