4ymr

Publication Abstract from PubMed

Sorting nexins (SNX) orchestrate membrane trafficking and signalling events required for the proper distribution of proteins within the endosomal network. Their phox homology (PX) domain acts as a phosphinositide (PI) recognition module that targets them to specific endocytic membrane domains. The modularity of SNX proteins confers a wide variety of functions from signalling to membrane deformation and cargo binding, and many SNXs are crucial modulators of endosome dynamics and are involved in a myriad of physiological and pathological processes such as neurodegenerative diseases, cancer and inflammation. Here, we have studied the poorly characterized SNX20 and its paralogue SNX21, which contain an N-terminal PX domain and a C-terminal PX-associated B (PXB) domain of unknown function. The two proteins share similar PI-binding properties and are recruited to early endosomal compartments by their PX domain. The crystal structure of the SNX21 PXB domain reveals a tetratricopeptide repeat (TPR) fold, a module that typically binds short peptide motifs, with three TPR alpha-helical repeats. However, the C-terminal capping helix adopts a highly unusual and potentially self-inhibitory topology. SAXS solution structures of SNX20 and SNX21 show that these proteins adopt a compact globular architecture, and membrane interaction analyses indicate the presence of overlapping PI-binding sites that may regulate their intracellular localisation. This study provides the first structural analysis of this poorly characterized subfamily of SNX proteins, highlighting a likely role as endosome-associated scaffolds.

Structure and membrane binding properties of the endosomal tetratricopeptide repeat (TPR) domain-containing sorting nexins SNX20 and SNX21.,Clairfeuille T, Norwood SJ, Qi X, Teasdale RD, Collins BM J Biol Chem. 2015 Apr 16. pii: jbc.M115.650598. PMID:25882846^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.