Resolution of basic gonococcal outer membrane proteins by nonequilibrium pH gradient electrophoresis.

Area of Science:

• Microbiology
• Molecular Biology
• Protein Chemistry

Background:

• Neisseria gonorrhoeae exhibits distinct colonial variants (opaque and transparent).
• Outer membrane proteins (OMPs) play crucial roles in bacterial adhesion and host interactions.
• Understanding OMP properties is vital for deciphering gonococcal pathogenesis.

Purpose of the Study:

• To characterize and compare the outer membrane proteins of opaque and transparent variants of Neisseria gonorrhoeae.
• To investigate the charge properties of major surface proteins.
• To explore potential implications for bacterial adhesion and host cell interactions.

Main Methods:

• Two-dimensional electrophoresis (isoelectric focusing and SDS-PAGE) was employed.
• Nonequilibrium pH gradient electrophoresis was used to assess protein charge.
• Amino acid analysis was performed on the principal outer membrane protein.

Main Results:

• Most higher-molecular-weight OMPs focused sharply in the acidic region.
• The principal outer membrane protein (31 kDa) and opacity-associated proteins behaved as basic proteins.
• Three distinct opacity-associated heat-modifiable proteins were identified.
• No other significant differences in OMP composition between variants were observed.

Conclusions:

• The major surface proteins of Neisseria gonorrhoeae are unexpectedly basic.
• Partial amidation of acidic residues may contribute to the net positive charge of the principal OMP.
• These basic properties could influence intragonococcal adhesion and interactions with mammalian cells.