Genetic transformation of genes for protein II in Neisseria gonorrhoeae.

The protein II (PII) outer membrane proteins of Neisseria gonorrhoeae are a family of heat-modifiable proteins that are subject to phase variation, in which the synthesis of different PII species is turned on and off at a high frequency. Transformation of PII genes from a donor gonococcal strain into a recipient strain was detected with monoclonal antibodies specific for the PII proteins of the donor. Individual PII protein-expressing transformants generally bound only one donor-specific PII monoclonal antibody. Recovery of transformants expressing a donor-specific PII protein depended on the PII protein expression state of the donor: the transformed population bound only monoclonal antibodies specific for PII proteins that were expressed in the donor. Colony variants with an altered frequency of switching of PII protein expression were isolated, but the altered switch phenotype did not cotransform with the PII structural gene. These results provide genetic evidence that PII proteins are the products of different genes and that expressed and unexpressed forms of the PII gene are different from each other.