ClbN

ClbN is a gene located within the colibactin biosynthesis gene cluster, also known as the pks island, in certain strains of Escherichia coli and related Enterobacteriaceae. The pks island encodes enzymes responsible for the production of colibactin, a small-molecule genotoxin that can induce DNA damage in host cells.

The ClbN protein is predicted to participate in the late stages of colibactin assembly or maturation, but its exact biochemical function has not been clearly established. In current annotations, ClbN lacks a definitively assigned catalytic activity, and researchers describe its role as putative or poorly characterized. Despite this uncertainty, ClbN is typically considered part of the conserved core of the pks gene cluster carried by pks-positive strains.

Functionally, experimental data on ClbN are limited and context-dependent. Some studies suggest that disruption of clbN can affect colibactin-related phenotypes, while others observe variable effects depending on the genetic background and experimental system used. This reflects the broader challenge of linking individual biosynthetic genes to specific steps in the assembly and activity of colibactin.

Taxonomically, ClbN is associated with pks-containing strains of E. coli, which are found in both pathogenic and commensal lineages. The presence of the pks island, including clbN, has been studied for its potential links to host DNA damage and associations with colorectal cancer risk, though the precise contribution of ClbN to these outcomes remains to be fully clarified. Ongoing research aims to characterize its structure, interactions, and regulatory controls within the pks cluster.