Adsorption of the tailed mycoplasma virus L3 to cell membranes

The adsorption properties of the tailed bacteriophage L3 to Acholeplasma laidlawii cells were studied. Adsorption followed a biphasic curve. Reversibility and virus heterogeneity were not sufficient to explain the break in the adsorption curve. Binding studies showed that each colony-forming unit could bind about 350 virions. The electrostatic nature of L3 adsorption was indicated by the effect of cations, pH, and temperature on the adsorption rate constant. L3 adsorption appeared to have a requirement for Ca2+, which could not be replaced by the mono- and divalent cations examined. Ethylene glycol-bis(beta-aminoethyl ether)-N,N-tetraacetic acid inhibition of adsorption was totally reversed by added Ca2+. The effects of EDTA, proteases, and lectins on absorption indicated that membrane proteins are the L3 receptors. The model for L3 adsorption is a multivalent one involving lateral diffusion of adsorbed virions and receptor proteins.