The phosphoinositide binding Phox Homology domain of Sorting Nexin 14
The PX domain is a phosphoinositide (PI) binding module present in many proteins with diverse functions. Sorting nexins (SNXs) make up the largest group among PX domain containing proteins. They are involved in regulating membrane traffic and protein sorting in the endosomal system. The PX domain of SNXs binds PIs and targets the protein to PI-enriched membranes. SNXs differ from each other in PI-binding specificity and affinity, and the presence of other protein-protein interaction domains, which help determine subcellular localization and specific function in the endocytic pathway. SNX14 may be involved in recruiting other proteins to the membrane via protein-protein and protein-ligand interaction. It is expressed in the embryonic nervous system of mice, and is co-expressed in the motoneurons and the anterior pituary with Islet-1. SNX14 shows a similar domain architecture as SNX13, containing an N-terminal PXA domain, a regulator of G protein signaling (RGS) domain, a PX domain, and a C-terminal domain that is conserved in some SNXs.
Feature 1:phosphoinositide binding site [chemical binding site]
Comment:A majority of PX domain containing proteins binds phosphatidylinositol-3-phosphate (PI3P) at this site. In some cases, other phosphoinositides, such as PI4P or PI(3,4)P2, are the preferred substrates.
Comment:based on the structures of phosphatidylinositol-3-phosphate bound to other members of this superfamily
Comment:Two basic residues are key in binding with phosphoinositides: one forms hydrogen bonds with the 3-phosphate of PI(3)P and another forms hydrogen bonds with the 4-and 5-hydroxyl groups of PI(3)P.