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The virulence-associated gonococcal H.8 gene encodes 14 tandemly repeated pentapeptides
W Baehr1, E C Gotschlich, P J Hitchcock
1Laboratory of Microbial Structure and Function, National Institutes of Allergy and Infectious Diseases.
Abstract:
H.8 is a virulence-associated, surface-exposed immunogenic macromolecule composed of lipid and protein, common to Neisseria gonorrhoeae and Neisseria meningitidis. The H.8 DNA sequence predicted a 6.9 kD peptide comprising 14 tandemly repeated pentameric sequences. Ten were identical: Pro, Ala, Ala, Glu, Ala. Also predicted was a lipoprotein leader consensus sequence which probably specified acylation since the Escherichia coli-expressed protein was tightly associated with lipid. Lipid appeared to contribute significantly to H.8 antigen's electrophoretic mobility. This is the first description of a prokaryotic outer membrane protein composed solely of tandem repeats. Furthermore, DNA encoding this repeat appears to have been duplicated and translocated into another neisserial gene encoding an azurin.
Insights
Neisseria gonorrhoeae and Neisseria meningitidis share the H.8 macromolecule, a surface protein. Its unique structure, composed of tandem repeats and lipid, is crucial for virulence and antigenicity.
Area of Science:
- Microbiology
- Molecular Biology
- Immunology
Background:
- H.8 is a shared surface macromolecule in Neisseria gonorrhoeae and Neisseria meningitidis.
- It is associated with virulence and is immunogenic, making it a target for immune responses.
Purpose of the Study:
- To characterize the structure and composition of the H.8 macromolecule.
- To investigate the genetic basis and potential evolutionary origins of the H.8 antigen.
Main Methods:
- DNA sequencing to predict the peptide sequence of H.8.
- Expression of the H.8 protein in Escherichia coli to study its association with lipids.
- Analysis of protein-lipid interactions and electrophoretic mobility.
Main Results:
- The H.8 DNA sequence encodes a 6.9 kD peptide with 14 tandemly repeated pentameric sequences.
- A lipoprotein leader sequence suggests lipid acylation, contributing to tight lipid association and altered electrophoretic mobility.
- This represents the first described prokaryotic outer membrane protein solely composed of tandem repeats.
Conclusions:
- The H.8 antigen's unique repetitive structure and lipid modification are key features.
- The duplication and translocation of H.8 repeat DNA into the azurin gene suggest potential gene evolution mechanisms in Neisseria.