Conformational Ensembles from Experimental Data and Computer Simulations

Conformational Ensembles from Experimental Data and Computer Simulations

Poster Abstracts

94-POS Board 14 C-edge Loops of Arrestin Function as a Membrane Anchor Ciara Lally 1 , Brian Bauer 1 , Jana Selent 2 , Martha Sommer 1 . 1 Charité Medical University, Berlin, Germany, 2 Pompeu Fabra University, Hospital del Mar Medical Research Institute, Barcelona, Spain. Over 800 different G-protein-coupled receptors (GPCRs) are present in the human body and regulate a wide variety of sensory and physiological responses. Signalling of these membrane proteins is attenuated by a two-step mechanism entailing receptor phosphorylation by a kinase followed by receptor binding by the protein arrestin. During formation of the arrestin–receptor complex, arrestin interacts with the phosphorylated receptor C terminus in a pre-complex, which activates arrestin for tight receptor binding. Although the first crystal structure of a GPCR- arrestin complex was recently published [1], the structure of the pre-complex and how it transitions to a high-affinity complex is poorly understood. Here we present molecular dynamics simulations and site-directed fluorescence experiments on arrestin-1 interactions with the GPCR rhodopsin, showing that loops within the C-edge of arrestin function as a membrane anchor. Activation of arrestin by receptor-attached phosphates is necessary for C-edge engagement of the membrane, and we show that these interactions are distinct in the pre-complex and high-affinity complex in regard to their conformation and orientation. Our results expand current knowledge of C-edge structure and further illuminate the conformational transitions that occur in arrestin along the pathway to tight receptor binding [2]. 1. Kang, Y., et al., Crystal structure of rhodopsin bound to arrestin by femtosecond X-ray laser. Nature, 2015. 523(7562): p. 561-7. 2. Lally, C.C., et al., C-edge loops of arrestin function as a membrane anchor. Nat Commun, 2017. 8: p. 14258.

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