Cheng Y.-S.Shi Z.Doudeva L.G.Yang W.-Z.Chak K.-F.Yuan H.S.2019-07-222019-07-22200600222836https://scholars.lib.ntu.edu.tw/handle/123456789/414376ColE7 is a nuclease-type colicin released from Escherichia coli to kill sensitive bacterial cells by degrading the nucleic acid molecules in their cytoplasm. ColE7 is classified as one of the group A colicins, since the N-terminal translocation domain (T-domain) of the nuclease-type colicins interact with specific membrane-bound or periplasmic Tol proteins during protein import. Here, we show that if the N-terminal tail of ColE7 is deleted, ColE7 (residues 63-576) loses its bactericidal activity against E. coli. Moreover, TolB protein interacts directly with the T-domain of ColE7 (residues 1-316), but not with the N-terminal deleted T-domain (residues 60-316), as detected by co-immunoprecipitation experiments, confirming that the N-terminal tail is required for ColE7 interactions with TolB. The crystal structure of the N-terminal tail deleted ColE7 T-domain was determined by the multi-wavelength anomalous dispersion method at a resolution of 1.7 ?. The structure of the ColE7 T-domain superimposes well with the T-domain of ColE3 and TR-domain of ColB, a group A Tol-dependent colicin and a group B TonB-dependent colicin, respectively. The structural resemblance of group A and B colicins implies that the two groups of colicins may share a mechanistic connection during cellular import. ? 2005 Elsevier Ltd. All rights reserved.Colicin structureColicin translocation domainCrystal structureMembrane translocationProtein cellular importjournal article10.1016/j.jmb.2005.11.0562-s2.0-30344457337https://www.scopus.com/inward/record.uri?eid=2-s2.0-30344457337&doi=10.1016%2fj.jmb.2005.11.056&partnerID=40&md5=b9d7300024e17ae63ca514f77bf3712a