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Published on: October 24, 2010
Identification of an iron-regulated 37,000-dalton protein in the cell envelope of Neisseria gonorrhoeae
Abstract:
We examined the outer membrane proteins which appear during the growth of Neisseria gonorrhoeae F62 in complex medium supplemented with 25 microM Desferal mesylate, a potent iron chelator. Outer membranes were prepared by Sarkosyl extraction and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Several higher-molecular-weight (74,000 to greater than 94,000) proteins increased under iron-limiting conditions. In addition we observed the appearance of an iron-regulated protein with an apparent molecular weight of 37,000. This protein comigrated with the gonococcal protein I under normal Laemmli gel conditions. By increasing the ionic strength of the lower gel buffer, separation of protein I and the 37,000-dalton iron-regulated protein occurred. The 37,000-dalton protein stained poorly with Coomassie blue. However, when a silver stain was used, the protein appeared as a major component of the gonococcal outer membrane. Production of this 37,000-dalton protein was suppressed by the addition of iron to the medium. An iron-regulated protein with a similar molecular weight was observed in four clinical isolates and in an additional laboratory strain. Peptide mapping indicated that the 37,000-dalton protein was distinct from protein I and was identical between strains of the WI and WII serogroups.
Insights
Neisseria gonorrhoeae outer membranes show increased high-molecular-weight proteins and a novel 37,000-dalton iron-regulated protein under iron-limiting conditions. This distinct protein is present across various strains, highlighting its importance in gonococcal iron acquisition.
Area of Science:
- Microbiology
- Protein Biochemistry
- Molecular Biology
Background:
- Neisseria gonorrhoeae requires iron for growth and virulence.
- Outer membrane proteins play crucial roles in bacterial adaptation and pathogenesis.
- Iron availability significantly influences the expression of Neisseria gonorrhoeae outer membrane proteins.
Purpose of the Study:
- To investigate the changes in outer membrane proteins of Neisseria gonorrhoeae F62 under iron-limiting conditions.
- To identify and characterize novel iron-regulated proteins in Neisseria gonorrhoeae.
- To compare the expression of these proteins across different strains.
Main Methods:
- Growth of Neisseria gonorrhoeae F62 in complex medium with Desferal mesylate (iron chelator).
- Isolation of outer membranes via Sarkosyl extraction.
- Analysis of protein profiles using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE).
- Protein identification using Coomassie blue and silver staining, and peptide mapping.
Main Results:
- Increased expression of higher-molecular-weight proteins (74,000–>94,000 Da) under iron limitation.
- Identification of a novel 37,000-Da iron-regulated protein.
- Separation of the 37,000-Da protein from Protein I by adjusting gel buffer ionic strength.
- The 37,000-Da protein was a major component, detected by silver stain, and its production was suppressed by iron.
- Similar iron-regulated proteins were found in clinical isolates and other laboratory strains.
- Peptide mapping confirmed the 37,000-Da protein is distinct from Protein I and conserved across serogroups.
Conclusions:
- Iron limitation induces significant changes in Neisseria gonorrhoeae outer membrane protein composition.
- A novel 37,000-Da iron-regulated protein is identified and characterized.
- This protein is distinct from Protein I and conserved among different Neisseria gonorrhoeae strains, suggesting a critical role in iron acquisition.
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