Insulin receptor-related receptor (IRR) is a receptor tyrosine kinase of the insulin receptor family. Although, IRR was discovered in 1989, no endogenous ligands for IRR have been identified, and a physiological role of the protein has remained uncertain for a long time. Therefore, it was attributed to proteins, which are called orphan. In 2005, for the first time, researchers at the IBCh RAS showed that this protein activates exclusively when the acid-base balance changes. The unusual functional properties of the receptor have attracted the attention of researchers around the world, but its structure was, for the first time, determined in the Institute of Crystallography with the co-authors from other organizations only in 2019 by small angle X-ray scattering (SAXS) and atomic force microscopy (AFM), finally eliminating this protein from the category of orphan ones.
Orphan protein takes а shape