Lactoferrin binding to lysozyme-treated Micrococcus luteus.

When the cell lysis of Micrococcus luteus by hen egg white or human lysozyme is performed in the presence of bovine or human lactoferrin, a temporary increase of the turbidity of the solution as followed at 450 nm is observed. Examination of the suspension under light microscopy has proven that the protoplasts produced upon lysozyme action are agglutinated by lactoferrin. The rate of agglutination depends on pH, lactoferrin, lysozyme and cells concentrations. Agglutination is maximal at pH 5.5. Around 1.4 X 10(6) binding sites for lactoferrin per cell have been determined through a Scatchard plot analysis. The binding to the cells is not mediated by the glycosidic moiety of lactoferrin but rather by a charge-to charge interaction as succinylation of about four out of the 39 lysines of lactoferrin completely abolishes its ability to agglutinate the cells. Binding does not depend on ionic iron nor on the iron content of lactoferrin itself.