A cooperative group of proteins that work together to protect cells from acid stress has been found in bacteria that transit through the human digestive tract, as reported online this week in Nature Chemical Biology.

When proteins encounter highly acidic environments, their normally stable structure can fall apart; if enough proteins lose their structure, the cell cannot operate normally and will die. Chaperones are a family of proteins that protect other proteins from losing their structure or help the proteins to regain their structure once lost.

Zengyi Chang, Peng Chen and colleagues look for ‘clients’ – or preferred protein substrates – of one of these chaperones by using a newly-designed non-natural amino acid to link the chaperone and its client together, allowing them to be identified as interacting. Among the clients, the authors discovered two more chaperones that subsequent tests demonstrated were working together with the initial chaperone to help other proteins more quickly regain their shape. This cooperative mechanism explains how bacteria might recover from their acidic travels.