The colibactin island (pks) of Escherichia coli formed by 19 genes (55-Kb), encodes nonribosomal peptide (NRP) and polyketide (PK) synthases, which allow the synthesis of colibactin,
a suspected hybrid PK-NRP compound that causes damage to DNA in eukaryotic cells. The clbP,
an unusual essential gene, is found in the operon structure with the clbS gene in the pks-encoded
machinery. Interestingly, the clbP gene has been annotated as a β-lactamase but no previous study has
reported its β-lactamase characteristics. In this study, we (i) investigated the β-lactamase properties
of the clbP gene in silico by analysing its phylogenetic relationship with bacterial β-lactamase
and peptidase enzymes, (ii) compar... More
The colibactin island (pks) of Escherichia coli formed by 19 genes (55-Kb), encodes nonribosomal peptide (NRP) and polyketide (PK) synthases, which allow the synthesis of colibactin,
a suspected hybrid PK-NRP compound that causes damage to DNA in eukaryotic cells. The clbP,
an unusual essential gene, is found in the operon structure with the clbS gene in the pks-encoded
machinery. Interestingly, the clbP gene has been annotated as a β-lactamase but no previous study has
reported its β-lactamase characteristics. In this study, we (i) investigated the β-lactamase properties
of the clbP gene in silico by analysing its phylogenetic relationship with bacterial β-lactamase
and peptidase enzymes, (ii) compared its three-dimensional (3D) protein structure with those of
bacterial β-lactamase proteins using the Phyr2 database and PyMOL software, and (iii) evaluated
in vitro its putative enzymatic activities, including β-lactamase, nuclease, and ribonuclease using
protein expression and purification from an E. coli BL21 strain. In this study, we reveal a structural
configuration of toxin/antitoxin systems in this island. Thus, similar to the toxin/antitoxin systems,
the role of the clbP gene within the pks-island gene group appears as an antitoxin, insofar as it is
responsible for the activation of the toxin, which is colibactin. In silico, our analyses revealed that
ClbP belonged to the superfamily of β-lactamase, class C. Furthermore, in vitro we were unable to
demonstrate its β-lactamase activity, likely due to the fact that the clbP gene requires co-expression
with other genes, such as the genes present in the pks-island (19 genes). More research is needed to
better understand its actions, particularly with regards to antibiotics, and to discover whether it has
any additional functions due to the importance of this gene and its toxicity.
