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J. Mol. Micro. Biotechnol. 3: 361-370
Facilitation of Bacteriophage Lambda DNA Injection by Inner Membrane Proteins of the Bacterial Phosphoenol-pyruvate:Carbohydrate Phosphotransferase System (PTS)
Margarita Esquinas-Rychen and Bernhard Erni
Infection of Escherichia coli by bacteriophage lambda depends on two membrane protein complexes: (i) maltoporin (LamB) in the outer membrane for adsorption and (ii) the IICMan-IIDMan complex of the mannose transporter in the inner membrane for DNA penetration. IICMan and IIDMan are components of the phosphoenolpyruvate: sugar phosphotransferase system (PTS) which together with the IIABMan subunit mediate transport and phosphorylation of sugars. To identify structural determinants important for penetration of lambda DNA, the homologous IIC-IID complexes of E. coli, K. pneumoniae and B. subtilis, and chimeric complexes between the IIC and IID were characterized. All three complexes support sugar transport in E. coli. Only IIC-IID of E. coli and B. subtilis also support bacteriophage lambda infection. The six chimeric complexes had lost transport activity, but three containing IIC of E. coli or B. subtilis continue to support bacteriophage lambda infection. Complexes containing IICMan and fusion proteins between truncated IIDMan and alkaline phosphatase or bgalactosidase support penetration of lambda DNA if less than 100 residues are missing from the C-terminus of IIDMan. Truncation of IICMan renders the complex unstable. Taken together, these results suggest, that IIC is the major specificity determinant for lambda infection but that the IIC subunit is stably expressed only in a complex with the IID subunit. Lambda DNA in transit across the periplasmic space, but not transforming plasmid DNA, is inaccessible to the non-specific nuclease NucA of Anabaena sp. targeted to the periplasmic space either in soluble form or as a fusion protein to the C-terminus of IIDMan. -
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