Nanopores: maltoporin channel as a sensor for maltodextrin and lambda-phage
1 Institut Pharmacologie & Biologie Structurale-CNRS UMR5089, 205, rte de Narbonne, F-31077 Toulouse, France
2 Lehrstuhl für Biotechnologie, Biozentrum, Am Hubland, D-97074 Würzburg, Germany
3 Inserm U-570, CHU Necker-Enfants Malades, 156, rue de Vaugirard, F- 75730 Paris Cedex 15, France
4 International University Bremen, School of Engineering and Science, D-28727 Bremen, Germany
Journal of Nanobiotechnology 2005, 3:3 doi:10.1186/1477-3155-3-3Published: 2 March 2005
To harvest nutrition from the outside bacteria e.g. E. coli developed in the outer cell wall a number of sophisticated channels called porins. One of them, maltoporin, is a passive specific channel for the maltodextrin uptake. This channel was also named LamB as the bacterial virus phage Lambda mis-uses this channel to recognise the bacteria. The first step is a reversible binding followed after a lag phase by DNA injection. To date little is known about the binding capacity and less on the DNA injection mechanism. To elucidate the mechanism and to show the sensitivity of our method we reconstituted maltoporin in planar lipid membranes. Application of an external transmembrane electric field causes an ion current across the channel. Maltoporin channel diameter is around a few Angstroem. At this size the ion current is extremely sensitive to any modification of the channels surface. Protein conformational changes, substrate binding etc will cause fluctuations reflecting the molecular interactions with the channel wall. The recent improvement in ion current fluctuation analysis allows now studying the interaction of solutes with the channel on a single molecular level.
We could demonstrate the asymmetry of the bacterial phage Lambda binding to its natural receptor maltoporin.
We suggest that this type of measurement can be used as a new type of biosensors.