4eo1
crystal structure of the TolA binding domain from the filamentous phage IKe
Structural highlights
FunctionG3P_BPIKE Plays essential roles both in the penetration of the viral genome into the bacterial host via pilus retraction and in the extrusion process. During the initial step of infection, G3P mediates adsorption of the phage to its primary receptor, the tip of host F-pilus. Subsequent interaction with the host entry receptor tolA induces penetration of the viral DNA into the host cytoplasm. In the extrusion process, G3P mediates the release of the membrane-anchored virion from the cell via its C-terminal domain (By similarity). Publication Abstract from PubMedFilamentous phage use the two N-terminal domains of their gene-3-proteins to initiate infection of Escherichia coli. One domain interacts with a pilus, and then the other domain binds to TolA at the cell surface. In phage fd, these two domains are tightly associated with each other, which renders the phage robust but non-infectious, because the TolA binding site is inaccessible. Activation for infection requires partial unfolding, domain disassembly and prolyl isomerization. Phage IKe infects E. coli less efficiently than phage fd. Unlike in phage fd, the pilus- and TolA-binding domains of phage IKe are independent of each other in stability and folding. The site for TolA binding is thus always accessible, but the affinity is very low. The structures of the two domains, analysed by X-ray crystallography and by NMR spectroscopy, revealed a unique fold for the N-pilus-binding domain and a conserved fold for the TolA-binding domain. The absence of an activation mechanism as in phage fd and the low affinity for TolA probably explain the low infectivity of phage IKe. They also explain why, in a previous co-evolution experiment with a mixture of phage fd and phage IKe, all hybrid phage adopted the superior infection mechanism of phage fd. Structural and energetic basis of infection by the filamentous bacteriophage IKe.,Jakob RP, Geitner AJ, Weininger U, Balbach J, Dobbek H, Schmid FX Mol Microbiol. 2012 May 17. doi: 10.1111/j.1365-2958.2012.08079.x. PMID:22591114[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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