Molecular interaction between bacteriophage and the gram-negative cell envelope

Conclusions Accumulation of molecular data on rceptor recognition by phages over the last years has provided some insight into the underlying molecular mechanisms. Some common motifs emerge. The receptor-recognizing areas of phage proteins seem to be confined to single regions on the polypeptide chains. The repeat structure of these regions, as found in T-even-type phages, seems to be specific for this group since it is not found in other phages such as lambda, T5, and BF23. The maximal number of surface exposed loops of receptor proteins recognized by the phages appears to be limited to four loops. The knowledge of X-ray structures and multiple alignment calculations of related receptor proteins will soon provide exact topological models of these proteins. These models will make possible the positioning of the receptor-binding proteins with respect to the surface-exposed loops involved in phage reception. The knowledge of the exact nature of mutations with new host-ranges will be of great value for such positioning.The TonB-dependent receptor proteins are a group of transport proteins which appear able to undergo considerable conformational changes not only during transport but also during phage adsorption. The isolation of receptor missense mutations impaired solely in phage reception should be very rewarding for TonB-dependent phages, since this could possibly lead to the identification of transiently surface-exposed loops of the receptor proteins.As for DNA uptake, the biochemical and biophysical characterization of pore-forming phage proteins should help elucidate the molecular mechanism of membrane penetration. Studies of this mechanism will be very much facilitated by the accessibilities of the corresponding genes to modern molecular biology techniques.Abbreviation aa amino acid(s)