Structural studies of integral membrane GPCR accessory proteins
<p>GPCR accessory proteins regulate the strength, efficiency and specificity of signal transfer upon receptor activation. Due to the inherent difficulties of studying membrane proteins <em>in vitro</em> and <em>in vivo</em>, little is known about the structure and topol...
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| Format: | Thesis |
| Language: | English |
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2013
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| Summary: | <p>GPCR accessory proteins regulate the strength, efficiency and specificity of signal transfer upon receptor activation. Due to the inherent difficulties of studying membrane proteins <em>in vitro</em> and <em>in vivo</em>, little is known about the structure and topology of these small accessory proteins. Two examples of GPCR accessory proteins are the Melanocortin-2 receptor accessory protein (MRAP) and the Receptor-activity-modifying protein (RAMP) family. MRAP and RAMP1 are the main focus of this thesis in which they are thoroughly characterised by solution-state NMR and further biophysical techniques.</p><p>The single-pass transmembrane domain protein MRAP regulates the class A GPCR melanocortin receptors. It is specifically required for trafficking the melanocortin-2-receptor from the endoplasmic reticulum to the cell surface and subsequent receptor activation. A remarkable characteristic of MRAP is its proposed native dual-topology, which leads to an antiparallel homodimeric conformation. Investigation of the biochemical and biophysical properties of MRAP revealed an α-helical transmembrane domain, and an α-helical N-terminal LD(Y/I)L-motif. Further efforts concentrated on establishing the homodimeric conformation of MRAP <em>in vitro</em>.</p><p> RAMP1 facilitates receptor trafficking and alters the ligand specificity of the GPCR Class B receptors calcitonin receptors and calcitonin receptor-like receptors. Moreover, RAMP1 is required to act as a Calcitonin-gene-related peptide (CGRP) receptor (RAMP1). RAMP1 has been shown to form stable parallel homodimers in the absence of its cognate receptor. Its dimerisation and the possible dimerisation motif PxxxxP-motif were studied extensively.</p><p>With the goal of understanding the mechanism of dimerisation and the role of GPCR accessory proteins I have used solution-state NMR in detergent micelles as my main technique. NMR provides unique possibilities for understanding the structure and dynamics of such small membrane proteins.</p> |
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