Insertional inactivation of the gene for the meningococcal lactoferrin binding protein.

The lactoferrin binding protein (LBP) of Neisseria meningitidis (the putative meningococcal receptor for human lactoferrin, LF), has been previously characterized as an outer-membrane protein of approximately 105 kDa. Using N-terminal amino acid sequence to generate an oligonucleotide probe, a clone from a lambda gt11 phage library was isolated. This clone was subjected to shuttle mutagenesis, in which an erythromycin mini-transposon was used to interrupt the LBP coding sequence. This insertion mutation was introduced into the meningococcus. A N. meningitidis strain that carried this transposon insertion no longer produced the 105 kDa protein. The absence of this protein was correlated with the inability to bind LF or to use LF as an iron source. The LBP mutant was able to grow with other Fe sources and demonstrated no other visible membrane protein alterations. These data confirm the suggestion that LBP is the meningococcal receptor.