4ymr
Crystal structure of the domain swapped PXB/TPR domain of mouse SNX21Crystal structure of the domain swapped PXB/TPR domain of mouse SNX21
Structural highlights
FunctionSNX21_MOUSE Binds to membranes enriched in phosphatidylinositol 3-phosphate (PtdIns(P3)) and phosphatidylinositol 4,5-bisphosphate (PubMed:25882846). May be involved in several stages of intracellular trafficking.[1] Publication Abstract from PubMedSorting 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[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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