Nectin, Membrane Protein Needed for Attachment of A TPase

We have isolated from Streptococcus faecalis plasma membranes a new protein, termed nectin, which is required for the attachment of the membrane enzyme, ATPase. Both nectin and membrane-bound ATPase are released from the native membranes by a procedure, described previously, which depends on repeated washing in dilute buffer without Mg++. Resolution of the solubilized nectin and ATPase can then be accomplished by gel filtration through agarose. The ATPase, separated from neck by passage through agarose, fails to reattach to enzyme-depleted membranes unless nectin is added. The amount of ATPase that recombines with the depleted membranes is proportional to the amount of nectin added until the membrane receptor sites for the enzyme become nearly saturated. Nectin is heat labile and has an ultraviolet absorption spectrum typical of a protein. By the method of gel filtration through Sephadex, we estimate that its molecular weight is 37,000.