BfpD

BfpD is a bacterial protein encoded by the bfpD gene, part of the bundle-forming pilus (BFP) operon found in enteropathogenic Escherichia coli (EPEC) and related pathogens. BFP are hair-like structures on the bacterial surface that mediate initial adherence to intestinal epithelial cells and facilitate microcolony formation, contributing to the localized adherence phenotype characteristic of EPEC infections.

Like other type IV pilus assembly proteins, BfpD functions as an ATPase that provides the energy for pilus polymerization. It is believed to reside in the cytoplasm and associate with inner membrane components of the BFP assembly machinery, becoming active through ATP binding and hydrolysis. The energy released by hydrolysis drives the addition of pilin subunits at the base of the growing pilus, enabling extension of the filament.

BfpD belongs to the family of secretion ATPases and contains the conserved Walker A and Walker B motifs typical of P-loop NTPases. Structural and sequence analyses indicate it forms oligomeric assemblies, often modeled as hexamers, which coordinate ATP hydrolysis during pilus assembly.

Expression of the BFP system, including bfpD, is regulated by transcription factors such as PerA in response to environmental cues. BFP production is generally characteristic of EPEC strains carrying the virulence plasmid that encodes the bfp operon and is linked to the bacterium's adherence strategy rather than toxin production alone.

Clinical relevance: presence of BFP and BfpD underpins the localized adherence pattern and is a key differentiator of EPEC from nonpathogenic E. coli strains. Disruption of bfpD or other BFP components impairs pilus assembly and adherence in laboratory studies.