Molecular basis for kinin selectivity and activation of the human bradykinin receptors

Cryo-EM structures of human type 1 and type 2 bradykinin receptors (B1R and B2R) reveal the basis for discrimination between the endogenous peptides des-Arg(10)-kallidin and bradykinin and their activation mechanism. Bradykinin and kallidin are endogenous kinin peptide hormones that belong to the kallikrein-kinin system and are essential to the regulation of blood pressure, inflammation, coagulation and pain control. Des-Arg(10)-kallidin, the carboxy-terminal des-Arg metabolite of kallidin, and bradykinin selectively activate two G protein-coupled receptors, type 1 and type 2 bradykinin receptors (B1R and B2R), respectively. The hyperactivation of bradykinin receptors, termed 'bradykinin storm', is associated with pulmonary edema in COVID-19 patients, suggesting that bradykinin receptors are important targets for COVID-19 intervention. Here we report two G protein-coupled complex structures of human B1R and B2R bound to des-Arg(10)-kallidin and bradykinin, respectively. Combined with functional analysis, our structures reveal the mechanism of ligand selectivity and specific activation of the bradykinin receptor. These findings also provide a framework for guiding drug design targeting bradykinin receptors for the treatment of inflammation, cardiovascular disorders and COVID-19.

Automated summary

The cryo-EM structures of human type 1 and type 2 bradykinin receptors provide insights into the mechanism of ligand selectivity and activation, offering potential targets for drug development in inflammation, cardiovascular disorders, and COVID-19 treatment.