The human LGR7 low-density lipoprotein class A module requires calcium for structure.

The relaxin and INSL3 receptors, LGR7 and LGR8, are the only human G-protein-coupled receptors to contain a low-density lipoprotein class-A (LDL-A) module. LDL-A modules are well characterized in a variety of diverse biological functions that involve ligand binding to elicit a response. Common features of the LDL-A modules characterized to date are the conservation of three disulfide bonds and the structural arrangement around a bound calcium ion. In this study we recombinantly produce the human LGR7 LDL-A module for NMR studies and demonstrate that calicum is required for the module to form a stable and correctly folded structure.