PMID:10678980

Citation	Elkins, C, Morrow, KJ Jr and Olsen, B (2000) Serum resistance in Haemophilus ducreyi requires outer membrane protein DsrA. Infect. Immun. 68:1608-19
Abstract	Haemophilus ducreyi is resistant to killing by normal serum antibody and complement. We discovered an H. ducreyi outer membrane protein required for expression of serum resistance and termed it DsrA (for "ducreyi serum resistance A"). The dsrA locus was cloned, sequenced, and mutagenized. An isogenic mutant (FX517) of parent strain 35000 was constructed and characterized, and it was found to no longer express dsrA. FX517 was at least 10-fold more serum susceptible than 35000. DsrA was expressed by all strains of H. ducreyi tested, except three naturally occurring, avirulent, serum-sensitive strains. FX517 and the three naturally occurring dsrA-nonexpressing strains were complemented in trans with a plasmid expressing dsrA. All four strains were converted to a serum-resistant phenotype, including two that contained truncated lipooligosaccharide (LOS). Therefore, serum resistance in H. ducreyi does not require expression of full-length LOS but does require expression of dsrA. The dsrA locus from eight additional H. ducreyi strains was sequenced, and the deduced amino acid sequences were more than 85% identical. The major difference between the DsrA proteins was due to the presence of one, two, or three copies of the heptameric amino acid repeat NTHNINK. These repeats account for the variability in apparent molecular mass of the monomeric form of DsrA (28 to 35 kDa) observed in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Since DsrA is present in virulent strains, is highly conserved, and is required for serum resistance, we speculate that it may be a virulence factor and a potential vaccine candidate.
Links	PubMed PMC97321
Keywords	Amino Acid Sequence; Bacterial Outer Membrane Proteins/chemistry; Bacterial Outer Membrane Proteins/genetics; Bacterial Outer Membrane Proteins/physiology; Base Sequence; Blood Bactericidal Activity; Haemophilus ducreyi/immunology; Haemophilus ducreyi/pathogenicity; Humans; Lipopolysaccharides/analysis; Molecular Sequence Data
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
HAEDC:Q9K2H6		GO:0009279: cell outer membrane	ECO:0000314:		C		Fig 5 shows the SDS-PAGE and Western blot identifying DsrA. Figure caption includes details about preparation of outer membrane for experiment.	complete CACAO 5151
HAEDC:Q9K2H6		GO:0020012: evasion or tolerance of host immune response	ECO:0000315:		P		Figure 6 shows that the DsrA mutant has lower resistance to bactericidal killing than the wild-type organism. Figure 7 shows that complementation of the mutant restores resistance	complete CACAO 5379
HAEDC:Q9K2H6	part_of	GO:0009279: cell outer membrane	ECO:0000314: direct assay evidence used in manual assertion		C		Seeded From UniProt	complete
HAEDC:Q9K2H6	involved_in	GO:0020012: evasion or tolerance of host immune response	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete

References

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