BfpE

BfpE is a gene designation used in some Escherichia coli strains that carry the bundle-forming pilus (BFP) operon. In enteropathogenic E. coli (EPEC) and related pathogens, BFP is a virulence factor that promotes initial adherence to intestinal cells, and its genes are frequently located on the EAF plasmid. BfpE is commonly listed among the fimbrial genes associated with this locus, but its exact product and role are less well defined than those of the major pilin gene bfpA.

Molecularly, bfpE may be annotated as encoding a small pilin-like protein or an assembly factor. Depending on the strain and database, predictions for bfpE include a signal peptide and possible periplasmic localization, or may reflect truncated or divergent sequences that render the gene nonfunctional. As a result, the presence and integrity of bfpE can vary among isolates.

Functionally, if expressed, BfpE is hypothesized to contribute to pilus assembly or stability, potentially acting as a minor pilin or auxiliary component within the BFP structure. However, direct experimental confirmation of its role is limited and results are inconsistent across studies and strains.

Regulation of bfpE, when applicable, generally aligns with the BFP operon. Its transcription is influenced by regulators such as PerA, and by environmental cues that also affect BFP expression, including temperature and growth conditions. This co-regulation mirrors the broader control of adhesin-related genes within the operon.

Clinical significance and distribution: The bundle-forming pilus is a known virulence factor for adherence, but the specific contribution of bfpE remains uncertain. BfpE is primarily reported in annotations linked to EPEC/EPEC-related plasmids, with some strains lacking an intact version of the gene. Homologs may exist in related fimbrial systems, reflecting evolutionary diversification of pilus-associated genes.