Different contributions of the outer and inner R-core residues of lipopolysaccharide to the recognition by spike H and G proteins of bacteriophageφX174

The binding of spike H and G proteins of bacteriophage phiX174 with lipopolysaccharides (LPSs) were evaluated by a competitive enzyme-linked plate assay using the biotin-labeled LPS of Escherichia coli C, one of a host strain, and the non-labeled LPSs having different R-core polysaccharide lengths. H protein promptly decreased its affinity when some saccharide residues were truncated from the outer R-core. However, G protein showed significant affinity to the LPSs lacking all the residues of the outer R-core and some of the inner R-core. Thus, G protein rather than H protein well recognized the residues of the inner R-core of LPS.