FIGURE 1.

Putative structural arrangement of the different putative RXFP1 components. The RXFP1 receptor shows typical GPCR features as the seven transmembrane helices and exposes specific properties significant for LGRs in the class A GPCRs, such as a large extracellular part constituted by several interrelated domains. Their exact spatial arrangement to one another remains unknown, but it is assumed that the N-terminal LDLa domain interacts directly with extracellular loops (indicated by red arrows). The endogenous ligand relaxin, a peptide hormone, binds to the LRRD and simultaneously to the linker region.