Characterization of the IgA1 protease from the Brazilian purpuric fever strain F3031 of Haemophilus influenzae biogroup aegyptius

• Published in: FEMS microbiology letters 2005-09, Vol.250 (2), p.229-236
• Main Authors: McGillivary, Glen, Smoot, Laura M., Actis, Luis A.
• Format: Article
• Language: English
• Subjects: Bacterial Proteins - genetics; Bacterial Proteins - physiology; Bacteriology; Base Sequence; Binding Sites; Biological and medical sciences; Brazilian purpuric fever; Chloramphenicol O-Acetyltransferase - analysis; Cleavage; Cloning; Cloning, Molecular; Cluster analysis; Clustering; Deoxyribonucleic acid; DNA; DNA sequencing; DNA, Bacterial; Fever; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Bacterial; Gene Expression Regulation, Enzymologic; Genes, Reporter; Genomes; Haemophilus aegyptius; Haemophilus influenzae; Haemophilus influenzae - enzymology; Haemophilus influenzae - genetics; Hemin; Hemin - physiology; IgA1 protease; Immunoglobulin A; Iron - physiology; Microbiology; Molecular Sequence Data; Pathogenicity, virulence, toxins, bacteriocins, pyrogens, host-bacteria relations, miscellaneous strains; Promoter Regions, Genetic; Protease; Proteinase; Purpura; Repressor Proteins - genetics; Repressor Proteins - physiology; Serine Endopeptidases - genetics; Serine Endopeptidases - metabolism; Substrate Specificity; Subtraction; Transcription; Vascular diseases
• ISSN: 0378-1097; 1574-6968
• DOI: 10.1016/j.femsle.2005.07.010

Brazilian purpuric fever is a severe vascular disease caused by an invasive clone of Haemophilus influenzae biogroup aegyptius, which normally causes self-limiting eye infections. A previous genome subtraction procedure resulted in the isolation of a DNA fragment, which encodes a putative IgA1 protease, specific to the F3031 Brazilian purpuric fever type strain. Cloning and sequencing of the entire F3031 iga1 gene showed that the subtracted DNA fragment encompasses the iga1 region encoding the active site and the cleavage specificity determinant of the protein, which are different from the cognate regions of the proteases produced by other H. influenzae strains. Western and IgA cleavage assays together with clustering analysis showed that the F3031 IgA1 protease is most similar to the type 2 proteases produced by H. influenzae type c and e strains. Analysis of the promoter region of the F3031 iga1 gene revealed the presence of Fur binding sites. However, real-time PCR analysis and transcriptional fusion assays showed that the expression of iga1 is not regulated by iron or hemin under the conditions tested.