The extracellular loop 2 (ECL2) is the longest and the most diverse loop among class A G protein-coupled receptors (GPCRs). We propose a 7-cluster classification scheme of currently resolved ECL2 domains based on volume overlaps and their intermolecular interactions with the other GPCR regions.
See: A. Nicoli, A. Dunkel, T. Giorgino, C. de Graaf, and A. Di Pizio. A Classification Model for the Second Extracellular Loop of Class A GPCRs, Journal of Chemical Information and Modeling, 2022. doi:10.1021/acs.jcim.1c01056
Distinct clusters A to G have been assigned on the basis of volumetric overlaps. See the paper for details.
Select links under the ID column to download the corresponding PDB structure. Hovering under ECL2 provides a preview.