Molecular anatomy of the receptor binding module of a bacteriophage long tail fiber

Abstract

Tailed bacteriophages (phages) are one of the most abundant life forms on Earth. They encode highly efficient molecular machines to infect bacteria, but the initial interactions between a phage and a bacterium that then lead to irreversible virus attachment and infection are poorly understood. This information is critically needed to engineer machines with novel host specificities in order to combat antibiotic resistance, a major threat to global health today. The tailed phage T4 encodes a specialized device for this purpose, the long tail fiber (LTF), which allows the virus to move on the bacterial surface and find a suitable site for infection. Consequently, the infection efficiency of phage T4 is one of the highest, reaching the theoretical value of 1. Although the atomic structure of the tip of the LTF has been determined, its functional architecture and how interactions with two structurally very different Escherichia coli receptor molecules, lipopolysaccharide (LPS) and outer membrane protein C (OmpC), contribute to virus movement remained unknown. Here, by developing direct receptor binding assays, extensive mutational and biochemical analyses, and structural modeling, we discovered that the ball-shaped tip of the LTF, a trimer of gene product 37, consists of three sets of symmetrically alternating binding sites for LPS and/or OmpC. Our studies implicate reversible and dynamic interactions between these sites and the receptors. We speculate that the LTF might function as a "molecular pivot" allowing the virus to "walk" on the bacterium by adjusting the angle or position of interaction of the six LTFs attached to the six-fold symmetric baseplate.

Adapting a Phage to Combat Phage Resistance

“…The same ORFs were suggested to be related to host recognition according to the genomic data from a long-term study from nature [15]. The most understood phage tail structure is that of phage T4 [34,35]. In T4, the long tail fiber is a product of four different genes (and requires additional protein products to function).…”

On uncovering and understanding interactions between bacteriophages and bacteria

“…SMALPs seemingly confirmed this, as it showed T4 tail fibers that each appeared to separately bind to SMALPs ( Figure S1b-d). Interestingly, while some SMALPs seemed to interact with the distal tail tips, as is to be expected based on previous findings 343 , other SMALPs could be interpreted as interacting further up the tail fibers. The presence of (presumably cellular) debris and the small size prohibited accurate quantifications of this effect.…”

T4-like Bacteriophages Isolated from Pig Stools Infect Yersinia pseudotuberculosis and Yersinia pestis Using LPS and OmpF as Receptors

“…This step, which brings the phage closer to its host cell surface, is followed by an irreversible attachment of the short tail fibres (STFs) to LPS [ 36 ]. Among OMPs, OmpC, along with LPS, are well-known as the receptors of T4-like phages [ 36 , 37 , 38 ], and OmpF is found to be recognized by T2-like phages as a receptor [ 7 , 39 ].…”