Delineation of a unique protein-protein interaction site on the surface of the estrogen receptor

Structural Biology Laboratory, Chemistry Department, University of York, York YO10 5YW, United Kingdom.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 04/2005; 102(10):3593-8. DOI: 10.1073/pnas.0407189102
Source: PubMed


Recent studies have identified a series of estrogen receptor (ER)-interacting peptides that recognize sites that are distinct from the classic coregulator recruitment (AF2) region. Here, we report the structural and functional characterization of an ERalpha-specific peptide that binds to the liganded receptor in an AF2-independent manner. The 2-A crystal structure of the ER/peptide complex reveals a binding site that is centered on a shallow depression on the beta-hairpin face of the ligand-binding domain. The peptide binds in an unusual extended conformation and makes multiple contacts with the ligand-binding domain. The location and architecture of the binding site provides an insight into the peptide's ER subtype specificity and ligand interaction preferences. In vivo, an engineered coactivator containing the peptide motif is able to strongly enhance the transcriptional activity of liganded ERalpha, particularly in the presence of 4-hydroxytamoxifen. Furthermore, disruption of this binding surface alters ER's response to the coregulator TIF2. Together, these results indicate that this previously unknown interaction site represents a bona fide control surface involved in regulating receptor activity.

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Available from: Eckardt Treuter, Aug 07, 2015
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    • "Like other NHRs, the “E” domain of ER contains LBD (Figure 1(a)). It consists of 12 helices, contains hormone binding pocket, and is responsible for the most part of functions activated by ligand binding, such as coregulator binding to AF2 [32] and dimerization interface. While ERα and ERβ have both overlapping and unique functions, the overall homology between the ERα protein LBD and ERβ protein LBD does not exceed 55% [19]. "
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    ABSTRACT: The estrogen receptor (ER) mediates most of the biological effects of estrogens at the level of gene regulation by interacting through its site-specific DNA and with other coregulatory proteins. In recent years, new information regarding the dynamic structural nature of ER has emerged. The physiological effects of estrogen are manifested through ER's two isoforms, ER(α) and ER(β). These two isoforms (ER(α) and ER(β)) display distinct regions of sequence homology. The three-dimensional structures of the DNA-binding domain (DBD) and ligand-binding domain (LBD) have been solved, whereas no three-dimensional natively folded structure for the ER N-terminal domain (NTD) is available to date. However, insights about the structural and functional correlations regarding the ER NTD have recently emerged. In this paper, we discuss the knowledge about the structural characteristics of the ER in general and how the structural features of the two isoforms differ, and its subsequent role in gene regulation.
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    • "The 17 hydroxyl of E2's D-ring makes a hydrogen bond with His524 in -helix 11. As a consequence of these interactions, -helix 12 lies over the ligand-binding cavity and forms, together with -helices 3 and 5, a groove-binding site for the Leu- Xaa-Xaa-Leu-Leu motif of receptor co-activators like p160/SRC-1 (Kong et al., 2005; Cheskis et al 2003). In contrast, the side chain of partial agonists like 4-hydroxytamoxifen (OHT) partially pushes -helix 12 away, forcing it into a conformation in which it binds to the co-activator binding site and reduces the affinity for the co-activator. "
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    ABSTRACT: Because of the concern about environmental chemicals with oestrogenic and anti-oestrogenic effects, there is a need to construct biosensors for classifying such chemicals according to their effect on oestrogen receptor conformation. The conformation of the ligand-binding domains (LBD) of oestrogen receptor-alpha and -beta determine their transcription regulation activity. Some ligands, i.e., the natural oestrogen oestradiol, induce an active conformation allowing interaction with co-activators. In contrast, antagonists like ICI 182, 780, because of their bulky side chains, do not allow an alpha-helix 12 positioning compatible with co-activator binding. Another type of oestrogen receptor-ligand interactions, termed "passive antagonism", was first defined by X-ray crystal structure analysis of receptors in complex with the side chain-less 5,11-cis-diethyl-5,6,11,12-tetrahydrochrysene-2,8-diol (THC). We have now used the ability of peptides selected from phage-displayed peptide libraries to bind conformation specifically to oestrogen receptor-alpha and -beta LBDs to analyse conformations induced by THC and a group of chlorinated biphenyls and their aryl-hydroxylated metabolites, suspected of being environmental chemical disruptors. In oestrogen receptor-beta, THC defined a "passive antagonist" peptide recognition pattern, which was also induced by several antagonistic hydroxylated biphenyls, while a clearly different peptide recognition pattern was induced by their chlorinated agonistic counterparts. In oestrogen receptor-alpha, THC induced a conformation similar to that induced by oestriol and other oestrogen receptor-alpha agonists, which, as evaluated by site-directed mutagenesis, have a functionally important interaction with oestrogen receptor-alpha residue His524. We conclude that the peptide recognition pattern can be used to classify suspected environmental endocrine disruptors according the oestrogen receptor-alpha and -beta conformations they induce.
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    • "To evaluate the potential-binding properties of the two identified PRD sub-domains, we explored the X-ray structural data of interactions between ER and p160 coregulators . The H3–H5/H12 region was identified by Wärnmark et al. [23] as the TIF2 coactivator-binding domain, i.e. the NR-box2 (a property confirmed by Rodriguez et al. [27]) while the S1/S2 region was reported by Kong et al. [24] as a part of the binding domain for the II antagonist peptide (Fig. 4a and b, respectively). This observation in favor of at least two distinct modes of association with coregulators, is in agreement with experimental studies showing that p160 SRC-1 and the proline-rich coactivator PGC-1 differently interact with ER [28]. "
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