Kinetic Analysis of Bacteriophage Sf6 Binding to Outer Membrane Protein A Using Whole Virions

Natalia B. Hubbs; Mareena M. Whisby-Pitts; Jonathan L. McMurry

The current working model for Podoviridae attachment is a three step model [44] . In the first step the virion binds to LPS reversibly. In the second step there is likely an irreversible interaction with a secondary receptor. Third, the genome is translocated from the phage capsid into the cell concurrent with several conformational changes in virion structure. Hu et al. have shown that bacteriophage T7 [45] undergoes extensive structural remodeling during infection, particularly in the tail machinery. In summation, we propose a model in which Sf6: Omp receptor recognition is not solely based on kinetics, but likely also involves conformational changes induced when docking to a cell surface (Figure 4 ). Sf6 interacts with LPS first via its tailspikes [25, 44, 46] likely coming into contact with the host surface at an angle, as work with a closely related phage, P22, has shown [47] . Once Sf6 has cleaved enough LPS repeats [24, 48] , and is close enough to the surface of the cell it interacts with its secondary receptor, an Omp [25] . Upon interaction with Omps by the tail machinery, a conformational change in the phage is likely triggered. Amino acid substitutions in the loops of OmpA may affect the ability of the phage to adopt the correct conformation to promote channel formation, which is necessary to translocate the DNA genome [44, [49] [50] [51] . Although more work is necessary to discern a complete understanding of Sf6 (and Podoviridae) infection, the data presented here shed light on the kinetics of Sf6 and OmpA binding, which is an important step during host recognition. All of All rights reserved. No reuse allowed without permission.