Making Structural Sense of Dimerization Interfaces of Delta Opioid Receptor Homodimers
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- 作者：Jennifer M. Johnston ; Mahalaxmi Aburi ; Davide Provasi ; Andrea Bortolato ; Eneko Urizar ; Nevin A. Lambert ; Jonathan A. Javitch ; Marta Filizola
- 刊名：Biochemistry
- 出版年：2011
- 出版时间：March 15, 2011
- 年：2011
- 卷：50
- 期：10
- 页码：1682-1690
- 全文大小：932K
- 年卷期：v.50,no.10(March 15, 2011)
- ISSN：1520-4995
文摘
Opioid receptors, like other members of the G protein-coupled receptor (GPCR) family, have been shown to associate to form dimers and/or oligomers at the plasma membrane. Whether this association is stable or transient is not known. Recent compelling evidence suggests that at least some GPCRs rapidly associate and dissociate. We have recently calculated binding affinities from free energy estimates to predict transient association between mouse delta opioid receptor (DOR) protomers at a symmetric interface involving the fourth transmembrane (TM4) helix (herein termed 鈥?鈥?dimer). Here we present disulfide cross-linking experiments with DOR constructs with cysteines substituted at the extracellular ends of TM4 or TM5 that confirm the formation of DOR complexes involving these helices. Our results are consistent with the involvement of TM4 and/or TM5 at the DOR homodimer interface, but possibly with differing association propensities. Coarse-grained (CG) well-tempered metadynamics simulations of two different dimeric arrangements of DOR involving TM4 alone or with TM5 (herein termed 鈥?/5鈥?dimer) in an explicit lipid鈭抴ater environment confirmed the presence of two structurally and energetically similar configurations of the 4 dimer, as previously assessed by umbrella sampling calculations, and revealed a single energetic minimum of the 4/5 dimer. Additional CG umbrella sampling simulations of the 4/5 dimer indicated that the strength of association between DOR protomers varies depending on the protein region at the interface, with the 4 dimer being more stable than the 4/5 dimer.