The SOCS box domain of SOCS3: Structure and interaction with the elonginBC-cullin5 ubiquitin ligase

Babon, JJ; Sabo, JK; Soetopo, A; Yao, SG; Bailey, MF; Zhang, JG; Nicola, NA; Norton, RS

Author(s): Babon, JJ; Sabo, JK; Soetopo, A; Yao, SG; Bailey, MF; Zhang, JG; Nicola, NA; Norton, RS;
Details: Publication Year 2008-09-12,Volume 381,Issue #4,Page 928-940
Journal Title: JOURNAL OF MOLECULAR BIOLOGY
Publication Type: Journal Article
Abstract: Suppressor of cytokine signalling 3 (SOCS3) is responsible for regulating the cellular response to a variety of cytokines, including interleukin 6 and leukaemia inhibitory factor. Identification of the SOCS box domain led to the hypothesis that SOCS3 can associate with functional E3 ubiquitin ligases and thereby induce the degradation of bound signalling proteins. This model relies upon an interaction between the SOCS box, elonginBC and a cullin protein that forms the E3 ligase scaffold. We have investigated this interaction in vitro using purified components and show that SOCS3 binds to elonginBC and cullin5 with high affinity. The SOCS3-elonginBC interaction was further characterised by determining the solution structure of the SOCS box-elonginBC ternary complex and by deletion and alanine scanning mutagenesis of the SOCS box. These studies revealed that conformational flexibility is a key feature of the SOCS-elonginBC interaction. In particular, the SOCS box is disordered in isolation and only becomes structured upon elonginBC association. The interaction depends upon the first 12 residues of the SOCS box domain and particularly on a deeply buried, conserved leucine. The SOCS box, when bound to elonginBC, binds tightly to cullin5 with 100 nM affinity. Domains upstream of the SOCS box are not required for elonginBC or cullin5 association, indicating that the SOCS box acts as an independent binding domain capable of recruiting elonginBC and cullin5 to promote E3 ligase formation. (C) 2008 Elsevier Ltd. All rights reserved.
Publisher: ACADEMIC PRESS LTD ELSEVIER SCIENCE LTD
Keywords: PHYSIOLOGICAL NEGATIVE REGULATOR; COLONY-STIMULATING FACTOR; JANUS TYROSINE KINASE; CYTOKINE SIGNALING-3; SH2 DOMAIN; ELONGIN-C; UNSTRUCTURED INSERTION; CUL5-RBX2 MODULES; IN-VIVO; PROTEINS
Publisher's Version: https://doi.org/10.1016/j.jmb.2008.06.038
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Creation Date: 2008-09-12 12:00:00