Disease relevance of bfpA

• Molecular variation among type IV pilin (bfpA) genes from diverse enteropathogenic Escherichia coli strains [1].
• Striking sequence variation has previously been observed among type IV pilin genes of other gram-negative bacterial pathogens (e.g., Pseudomonas and Neisseria spp.). In contrast, the established sequences of bfpA genes from two distantly related prototype EPEC strains vary by only a single base pair [1].
• In this study, an isogenic mutant of enteropathogenic Escherichia coli (EPEC) was constructed containing the entire tcpA gene from Vibrio cholerae 0395, which encodes the major structural subunit of the toxin-coregulated pilus (TCP), in place of bfpA, which encodes the major structural subunit of the bundle-forming pilus (BFP) [2].

High impact information on bfpA

• Whether these pili are also required for virulence was tested in volunteers by inactivating bfpA or bfpT (perA) encoding, respectively, the pilus subunit and the bfp operon transcriptional activator [3].
• Isogenic strains mutated in perA (a transcriptional activator), bfpA (a type IV pilin), luxS (a quorum-sensing autoinducer gene) and in the type III secretion genes were reduced for motility in Dulbecco's modified Eagle medium (DMEM) motility agar and produced none or few flagella when associated with epithelial cells [4].
• Furthermore, it shares significant homology with a bfpA upstream AT-rich region, which has been shown to be involved in the BfpT-dependent regulation of bfpA [5].
• While bfpA::TnphoA mutants cannot be complemented for LA by plasmids carrying the bfpA gene alone in trans, this work shows that they can be complemented by plasmids carrying the bfpA gene, as well as approximately 10 kb of downstream sequence, suggesting that such mutations have polar effects on downstream genes [6].
• Cloning and characterization of bfpTVW, genes required for the transcriptional activation of bfpA in enteropathogenic Escherichia coli [7].

Biological context of bfpA

• BFP are polymers of bundlin, a pilin protein that is encoded by the bfpA gene found on a large EPEC plasmid [1].
• However, four strains lack most or all of these phenotypes despite having an intact bfpA gene [1].
• Deletion experiments led to the identification of a contiguous cluster of at least 12 open reading frames, including bfpA, that could direct the synthesis of a morphologically normal BFP filament [8].
• RFLP analysis resolved nine eae, nine bfpA, and four perA alleles [9].
• These results have important implications for our understanding of bundlin structure, transmission of the bfp gene cluster among EPEC strains, and the role of bundlin variation in the evasion of host immune system responses [1].

Anatomical context of bfpA

• Strains which did not express BFP induced significantly less cell death, including a bfpA disruptional mutant of E2348/69, EAF plasmid-cured E2348/69, HB101, and HB101 complemented with the locus of enterocyte effacement pathogenicity island [10].
• None of the serotypes behaved as EPEC, i.e. carried the eaeA, bfpA, and EAF DNA sequences simultaneously and presented localized adherence to HeLa cells [11].

Associations of bfpA with chemical compounds

• Replacement of either cysteine codon 129 or 179 of bfpA with a serine codon results in reduced levels of bundlin, similar to the effect of the dsbA mutation [12].
• We also found that association of prebundlin or bundlin with sucrose density flotation gradient fractions containing both inner and outer membrane proteins does not require any accessory proteins [13].

Other interactions of bfpA

• A series of deletions of the bfpA upstream promoter region was prepared; with respect to the bfpA transcription start site, sequence between nucleotides -94 and -55 was found to bind bfpT [7].
• When complemented with a larger fragment containing bfpP as well as bfpA, the mutant expresses the fully processed BfpA protein [14].
• Disruption of bfpB, the second open reading frame downstream of bfpA, was performed by allelic exchange [15].

Analytical, diagnostic and therapeutic context of bfpA

• Eight different bfpA alleles were identified by sequencing of the PCR products [1].
• Immunoblotting of whole cell lysates of BFP-positive, EAF-positive or -negative, and LA-positive or -negative EPEC strains revealed variations in the size (18,500-21,000) of the expressed structural subunit of BFP, suggesting differences in processing that may account for discrepancies between the bfpA, EAF, and LA [16].
• Because the bfpA probe consists primarily of sequences encoding an important EPEC virulence factor, in contrast to the unknown function of sequences contained in the EAF probe, the bfpA probe may be useful in epidemiologic studies to detect EPEC [16].

References