ProQ

ProQ is a bacterial RNA-binding protein of the FinO/ProQ family that functions as a global post-transcriptional regulator. It is found in many Gram-negative bacteria, with notable roles described in Enterobacterales such as Escherichia coli and Salmonella enterica. ProQ binds a wide range of RNA substrates, including structured noncoding RNAs and messenger RNAs, and influences RNA stability and translation. In many contexts ProQ operates alongside the Hfq RNA chaperone, but it can also act independently, expanding the regulatory repertoire beyond Hfq alone.

Structurally, ProQ comprises an N-terminal FinO-like domain, which mediates RNA binding, and a C-terminal region that contributes to RNA recognition and possibly interactions with other factors. The two-domain architecture allows ProQ to recognize structured RNA elements and to shape regulatory networks at the post-transcriptional level.

Biological impact attributed to ProQ includes modulation of virulence gene expression, outer membrane protein regulation, and responses to environmental stresses. In several studies, ProQ deficiency alters motility, biofilm formation, and pathogenic potential in infection models, illustrating its role in adaptation to changing conditions.

Despite advances, the full regulon and mechanism of action for ProQ remain areas of active research. High-throughput approaches have mapped numerous ProQ-RNA interactions, but there is ongoing work to distinguish direct regulatory effects from indirect consequences and to understand how ProQ cooperates with, or differs from, other RNA-binding proteins such as Hfq across diverse bacteria.