Cleavage of the protein III and major iron-regulated protein of Neisseria gonorrhoeae by lysosomal cathepsin G

J Gen Microbiol. 1987 Jan;133(1):155-62. doi: 10.1099/00221287-133-1-155.


Incubation of either 125I-labelled or unlabelled Neisseria gonorrhoeae with enzymically active preparations of human polymorphonuclear leucocyte lysosomal cathepsin G revealed that surface-exposed outer-membrane proteins were susceptible to proteolytic modification. Electroimmunoblotting experiments confirmed that outer-membrane protein III (PIII) and the major iron-regulated protein (MIRP), two conserved gonococcal proteins, were cleaved by cathepsin G. A direct relationship was observed between susceptibility to the antibacterial properties of cathepsin G and cleavage of PIII among isogenic strains differing in their level of resistance to the bactericidal activity of cathepsin G. Although the antibacterial property of cathepsin G is known to be independent of serine-esterase activity, the data suggest that gonococcal outer-membrane proteins are involved in the binding of cathepsin G, and that variation in the level of resistance reflects the degree to which target outer-membrane proteins such as PIII are exposed.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Autoradiography
  • Bacterial Outer Membrane Proteins / metabolism*
  • Cathepsin G
  • Cathepsins / metabolism*
  • Electrophoresis, Polyacrylamide Gel
  • Immunologic Techniques
  • Neisseria gonorrhoeae / metabolism*
  • Serine Endopeptidases


  • Bacterial Outer Membrane Proteins
  • Cathepsins
  • Serine Endopeptidases
  • CTSG protein, human
  • Cathepsin G