Insertional inactivation of the gene for the meningococcal lactoferrin binding protein

Area of Science:

• Microbiology
• Bacterial Pathogenesis
• Outer Membrane Proteins

Background:

• Neisseria meningitidis requires iron for growth and survival.
• Human lactoferrin (LF) is an iron-binding protein present in mucosal secretions.
• The lactoferrin binding protein (LBP) was hypothesized to be the meningococcal receptor for LF.

Purpose of the Study:

• To genetically confirm the function of the lactoferrin binding protein (LBP) in Neisseria meningitidis.
• To elucidate the role of LBP in lactoferrin binding and iron acquisition.

Main Methods:

• Isolation of a clone encoding LBP using an oligonucleotide probe derived from N-terminal amino acid sequence.
• Shuttle mutagenesis of the LBP gene using an erythromycin mini-transposon.
• Introduction of the transposon insertion into N. meningitidis.
• Analysis of LBP expression, LF binding, and iron utilization in the mutant strain.

Main Results:

• A transposon insertion successfully disrupted the LBP coding sequence in N. meningitidis.
• The LBP-deficient mutant failed to produce the 105 kDa outer membrane protein.
• The mutant strain exhibited a complete inability to bind human lactoferrin (LF).
• The LBP mutant could not utilize LF as an iron source for growth.
• No other significant alterations in membrane protein profiles were observed in the mutant.

Conclusions:

• Lactoferrin binding protein (LBP) is definitively confirmed as the meningococcal receptor for human lactoferrin.
• LBP plays a critical role in Neisseria meningitidis's ability to acquire iron from lactoferrin.
• Targeting LBP could represent a novel strategy for combating meningococcal infections.