The GPS motif is found in GPCRs, and is the site for auto-proteolysis, so is thus named, GPS [1,2,3,4]. The GPS motif is a conserved sequence of ~40 amino acids containing canonical cysteine and tryptophan residues, and is the most highly conserved part of the domain. In most, if not all, cell-adhesion GPCRs these undergo autoproteolysis in the GPS between a conserved aliphatic residue (usually a leucine) and a threonine, serine, or cysteine residue [5]. In higher eukaryotes this motif is found embedded in the C-terminal beta-stranded part of a GAIN domain - GPCR-Autoproteolysis INducing (GAIN). The GAIN-GPS domain adopts a fold in which the GPS motif, at the C-terminus, forms five beta-strands that are tightly integrated into the overall GAIN domain. The GPS motif, evolutionarily conserved from tetrahymena to mammals, is the only extracellular domain shared by all human cell-adhesion GPCRs and PKD proteins, and is the locus of multiple human disease mutations. The GAIN-GPS domain is both necessary and sufficient functionally for autoproteolysis, suggesting an autoproteolytic mechanism whereby the overall GAIN domain fine-tunes the chemical environment in the GPS to catalyse peptide bond hydrolysis [6]. In the cell-adhesion GPCRs and PKD proteins, the GPS motif is always located at the end of their long N-terminal extracellular regions, immediately before the first transmembrane helix of the respective protein.

1: Structural requirements for alpha-latrotoxin binding and alpha- latrotoxin-stimulated secretion. A study with calcium-independent receptor of alpha-latrotoxin (CIRL) deletion mutants. Krasnoperov V, Bittner MA, Holz RW, Chepurny O, Petrenko AG; J Biol Chem 1999;274:3590-3596. PMID:9920906

2: alpha-Latrotoxin receptor CIRL/latrophilin 1 (CL1) defines an unusual family of ubiquitous G-protein-linked receptors. G-protein coupling not required for triggering exocytosis. Sugita S, Ichtchenko K, Khvotchev M, Sudhof TC; J Biol Chem 1998;273:32715-32724. PMID:9830014

3: A latrophilin/CL-1-like GPS domain in polycystin-1. Ponting CP, Hofmann K, Bork P; Curr Biol 1999;26:585-588. PMID:10469603

4: Characterization of cis-autoproteolysis of polycystin-1, the product of human polycystic kidney disease 1 gene. Wei W, Hackmann K, Xu H, Germino G, Qian F; J Biol Chem. 2007;282:21729-21737. PMID:17525154

5: Post-translational proteolytic processing of the calcium-independent receptor of alpha-latrotoxin (CIRL), a natural chimera of the cell adhesion protein and the G protein-coupled receptor. Role of the G protein-coupled receptor proteolysis site (GPS) motif. Krasnoperov V, Lu Y, Buryanovsky L, Neubert TA, Ichtchenko K, Petrenko AG; J Biol Chem. 2002;277:46518-46526. PMID:12270923

6: A novel evolutionarily conserved domain of cell-adhesion GPCRs mediates autoproteolysis. Arac D, Boucard AA, Bolliger MF, Nguyen J, Soltis SM, Sudhof TC, Brunger AT; EMBO J. 2012;31:1364-1378. PMID:22333914