2jy7

File:2jy7.jpg

NMR structure of the ubiquitin associated (UBA) domain of p62 (SQSTM1). RDC refined

Overview

The p62 protein functions as a scaffold in signaling pathways that lead to activation of NF-kappaB and is an important regulator of osteoclastogenesis. Mutations affecting the receptor activator of NF-kappaB signaling axis can result in human skeletal disorders, including those identified in the C-terminal ubiquitin-associated (UBA) domain of p62 in patients with Paget disease of bone. These observations suggest that the disease may involve a common mechanism related to alterations in the ubiquitin-binding properties of p62. The structural basis for ubiquitin recognition by the UBA domain of p62 has been investigated using NMR and reveals a novel binding mechanism involving a slow exchange structural reorganization of the UBA domain to a "bound" non-canonical UBA conformation that is not significantly populated in the absence of ubiquitin. The repacking of the three-helix bundle generates a binding surface localized around the conserved Xaa-Gly-Phe-Xaa loop that appears to optimize both hydrophobic and electrostatic surface complementarity with ubiquitin. NMR titration analysis shows that the p62-UBA binds to Lys(48)-linked di-ubiquitin with approximately 4-fold lower affinity than to mono-ubiquitin, suggesting preferential binding of the p62-UBA to single ubiquitin units, consistent with the apparent in vivo preference of the p62 protein for Lys(63)-linked polyubiquitin chains (which adopt a more open and extended structure). The conformational switch observed on binding may represent a novel mechanism that underlies specificity in regulating signalinduced protein recognition events.

About this Structure

2JY7 is a Single protein structure of sequence from Homo sapiens. Full crystallographic information is available from OCA.

Reference

Ubiquitin Recognition by the Ubiquitin-associated Domain of p62 Involves a Novel Conformational Switch., Long J, Gallagher TR, Cavey JR, Sheppard PW, Ralston SH, Layfield R, Searle MS, J Biol Chem. 2008 Feb 29;283(9):5427-5440. Epub 2007 Dec 14. PMID:18083707 Page seeded by OCA on Sun May 4 09:23:29 2008

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