Attaches the circulating virion to the bacterial lipopolysaccharides which serve as receptor for the virus. Determines the phage host-range. Probably triggers with protein H the injection of the phage DNA into the host cytoplasm upon conformational changes induced by the interaction with host lipopolysaccharides (By similarity). The virion is composed of 60 copies each of the F, G, and J proteins, and 12 copies of the H protein. There are 12 spikes which are each composed of 5 G and one H proteins. Belongs to the microvirus G protein family.