TY - JOUR
T1 - The TolC protein of Escherichia coli serves as a cell-surface receptor for the newly characterized TLS bacteriophage
AU - German, Greg J.
AU - Misra, Rajeev
N1 - Funding Information:
We are grateful to Leanne Misra and Anne Marie Augustus for critically reading the manuscript, and to Christy Menor and Ammar Serge Hougeir for mutant analysis. We thank Chris Bartholomew for his assistance with electron microscopy. This work was supported, in part, by a grant (GM48167 to RM) from the National Institutes of Health and Arizona State University Student Government and Graduate College (to G.J.G.).
PY - 2001
Y1 - 2001
N2 - The TolC protein of Escherichia coli is implicated in a variety of diverse cellular functions, including antibiotic efflux and α-hemolysin secretion. An incidental role of TolC is to facilitate the entry of the bacteriophage TLS and colicin E1 into the bacterial cell. Despite the resolution of TolC's atomic structure, the roles of specific residues in its diverse functions are unknown. Here, we describe a genetic strategy for isolating missense tolC mutations that abolish the bacteriophage receptor activity of the TolC protein without influencing its role in antibiotic efflux. These spontaneous mutations affected two regions of the TolC protein and included base-pair substitutions, insertions, and deletions. Comparison of the TolC sequence with those of its homologues revealed two hypervariable stretches that were predicted to represent loops. Interestingly, all but one of the TolC alterations preventing phage binding were located in these two hypervariable regions, which are likely to be exposed on the cell surface. This was substantiated by the recently solved three-dimensional structure of TolC. Curiously, all the phage-resistant TolC mutants showed varying degrees of resistance to colicin E1, suggesting the involvement of overlapping regions of TolC in colicin E1 import and phage binding. The phage used in this study, TLS, was earlier reported as a strain of U3. However, we show here that, unlike the previously reported lipopolysaccharide-specific U3 phage, this phage displays a distinctly different host range and discrete morphological features and, in addition to utilizing TolC as receptor, it requires the inner core of a lipopolysaccharide.
AB - The TolC protein of Escherichia coli is implicated in a variety of diverse cellular functions, including antibiotic efflux and α-hemolysin secretion. An incidental role of TolC is to facilitate the entry of the bacteriophage TLS and colicin E1 into the bacterial cell. Despite the resolution of TolC's atomic structure, the roles of specific residues in its diverse functions are unknown. Here, we describe a genetic strategy for isolating missense tolC mutations that abolish the bacteriophage receptor activity of the TolC protein without influencing its role in antibiotic efflux. These spontaneous mutations affected two regions of the TolC protein and included base-pair substitutions, insertions, and deletions. Comparison of the TolC sequence with those of its homologues revealed two hypervariable stretches that were predicted to represent loops. Interestingly, all but one of the TolC alterations preventing phage binding were located in these two hypervariable regions, which are likely to be exposed on the cell surface. This was substantiated by the recently solved three-dimensional structure of TolC. Curiously, all the phage-resistant TolC mutants showed varying degrees of resistance to colicin E1, suggesting the involvement of overlapping regions of TolC in colicin E1 import and phage binding. The phage used in this study, TLS, was earlier reported as a strain of U3. However, we show here that, unlike the previously reported lipopolysaccharide-specific U3 phage, this phage displays a distinctly different host range and discrete morphological features and, in addition to utilizing TolC as receptor, it requires the inner core of a lipopolysaccharide.
KW - Antibiotic efflux
KW - Bacteriophage receptor
KW - Lipopolysaccharide
KW - Mutant analysis
KW - TolC
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U2 - 10.1006/jmbi.2001.4578
DO - 10.1006/jmbi.2001.4578
M3 - Article
C2 - 11350161
AN - SCOPUS:0034973115
SN - 0022-2836
VL - 308
SP - 579
EP - 585
JO - Journal of molecular biology
JF - Journal of molecular biology
IS - 4
ER -