Biophysical Society Thematic Meeting - October 13-15, 2015

Biophysics of Proteins at Surfaces: Assembly, Activation, Signaling

Poster Abstracts

1-POS Board 1 Helix 8 of the Angiotensin-II Type 1a Receptor Interacts With Phosphatidylinositol Phosphates and Modulates Membrane Insertion Daniel J. Hirst 1 , Tzong-Hsien Lee 1 , Walter G. Thomas 2 , Mibel Aguilar 1 . 1 Monash University, Clayton, Australia, 2 The University of Queensland, St Lucia, Vic, Australia. The carboxyl-terminus of the type 1 angiotensin II receptor (AT1A) regulates receptor activation/deactivation and the amphipathic Helix 8 within the carboxyl-terminus is a high affinity interaction motif for plasma membrane lipids. We have used dual polarisation interferometry [1] to examine the role of phosphatidylinositdes in the specific recognition of Helix 8 in the AT1A receptor. A synthetic peptide corresponding to Leu305 to Lys325 (Helix 8 AT1A) discriminated between PIPs and different charges on lipid membranes [2]. Peptide binding to PtdIns(4)P-containing bilayers caused a dramatic change in the birefringence (a measure of membrane order) of the bilayer. Kinetic modelling showed that PtdIns(4)P is held above the bilayer until the mass of bound peptide reaches a threshold, after which the peptides insert further into the bilayer. This suggests that Helix 8 can respond to the presence of PI(4)P by withdrawing from the bilayer, resulting in a functional conformational change in the receptor. 1. Lee TH, Hirst D, and Aguilar MI, ‘New Insights into the Molecular Mechanisms of Biomembrane Structural Changes and Interactions by optical biosensor technology’, BBA Biomembranes, in press, 2015. doi: 10.1016/j.bbamem.2015.05.012. 2. Hirst D, Lee TH, Pattenden LK, Thomas WG and Aguilar MI, “Helix 8 of the angiotensin-1a receptor interacts with phosphatidylinositol phosphates and modulates membrane insertion”. Scientific Reports, in press, 2015. DOI: 10.1038/srep09972.

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