Pathway I. Group A nuclease colicins parasitize and bind tightly (Kd ≤ 10−9 M) to the vitamin B12 receptor on which they diffuse laterally in the OM (outer membrane) and use their long (≥100 Å; 1 Å=0.1 nm) receptor-binding domain as a ‘fishing pole’ to locate the OmpF porin channel for translocation. Crystal structures of OmpF imply that a disordered N-terminal segment of the colicin T-domain initiates insertion. Pathway II. Colicin N does not possess a ‘fishing pole’ receptor-binding domain. Instead, it uses OmpF as the Omp (outer membrane protein) for reception and translocation, processes in which LPS (lipopolysaccharide) may also serve. Keio collection experiments defined the LPS core that is used. Pathway III. Colicin E1 utilizes the drug-export protein TolC for import. CD spectra and thermal-melting analysis predict: (i) N-terminal translocation (T) and central receptor (BtuB) -binding (R) domains are predominantly α-helical; and (ii) helical coiled-coil conformation of the R-domain is similar to that of colicins E3 and Ia. Recombinant colicin peptides spanning the N-terminal translocation domain defined TolC-binding site(s). The N-terminal 40-residue segment lacks the ordered secondary structure. Peptide 41–190 is helical (78%), co-elutes with TolC and occluded TolC channels. Driven by a trans-negative potential, peptides 82–140 and 141–190 occluded TolC channels. The use of TolC for colicin E1 import implies that the interaction of this colicin with the other Tol proteins does not occur in the periplasmic space, but rather through Tol domains in the cytoplasmic membrane, thus explaining colicin E1 cytotoxicity towards a strain in which a 234 residue periplasmic TolA segment is deleted.
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December 2012
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Conference Article|
November 21 2012
Pathways of colicin import: utilization of BtuB, OmpF porin and the TolC drug-export protein
Stanislav D. Zakharov;
Stanislav D. Zakharov
*Department of Biological Sciences, Hockmeyer Hall of Structural Biology, Purdue University, West Lafayette, IN 47907, U.S.A.
†Institute of Basic Problems of Biology, Russian Academy of Sciences, Pushchino, Moscow Region 140290, Russian Federation
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Onkar Sharma;
Onkar Sharma
‡Division of Infectious Diseases, Children's Hospital, Harvard Medical School, Boston, MA 02115, U.S.A.
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Mariya Zhalnina;
Mariya Zhalnina
*Department of Biological Sciences, Hockmeyer Hall of Structural Biology, Purdue University, West Lafayette, IN 47907, U.S.A.
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Eiki Yamashita;
Eiki Yamashita
§Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan
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William A. Cramer
William A. Cramer
1
*Department of Biological Sciences, Hockmeyer Hall of Structural Biology, Purdue University, West Lafayette, IN 47907, U.S.A.
1To whom correspondence should be addressed (emailwaclab@purdue.edu).
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Publisher: Portland Press Ltd
Received:
August 22 2012
Online ISSN: 1470-8752
Print ISSN: 0300-5127
© 2012 The Authors Journal
2012
Biochem Soc Trans (2012) 40 (6): 1463–1468.
Article history
Received:
August 22 2012
Citation
Stanislav D. Zakharov, Onkar Sharma, Mariya Zhalnina, Eiki Yamashita, William A. Cramer; Pathways of colicin import: utilization of BtuB, OmpF porin and the TolC drug-export protein. Biochem Soc Trans 1 December 2012; 40 (6): 1463–1468. doi: https://doi.org/10.1042/BST20120211
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