AatB

AatB is a protein encoded by the aatB gene in certain Gram-negative bacteria. It is associated with the Aat secretion system, a multi-component export system that transports specific substrates across the outer membrane. In many well-characterized systems, AatB is a periplasmic adaptor protein that is thought to link an inner membrane transporter to an outer membrane channel, forming a continuous conduit for substrates to reach the cell surface or exterior.

Structural and functional analyses suggest that AatB belongs to the family of periplasmic adaptor proteins and possesses the extended coiled-coil architecture typical of these proteins. It is commonly encoded in an operon with other aat genes, such as aatA and aatD, and its expression is often co-regulated with these components.

Distribution and significance: AatB homologs have been identified in several enteric pathogens, particularly within the family Enterobacteriaceae. The Aat secretion system is associated with virulence in some strains, aiding the secretion of virulence factors or adhesins. However, AatB is not essential for growth under laboratory conditions, and its contribution to fitness varies by species and environment.

Discovery and naming: The aat locus was described in comparative genomic studies of pathogenic Escherichia coli and related bacteria, with AatB serving as one of the core components in many annotations. Research continues to characterize its precise interactions and substrates.

See also: AatA, AatC, AatD.