G protein coupled receptors (GPCRs) are the largest family of proteins in the human genome and also the largest target for therapeutic drugs; thus they are of enormous scientific and practical interest. They are divided into a number of families. Of these, family-A is the best understood, but family-B includes receptors which are likely to be important in many disease states and so it is important to understand how these function, both to further our knowledge of fundamental biology and also for the design of new drugs. Calcitonin gene-related peptide (CGRP) is found throughout the nervous system and is particularly important in regulating both the cardiovascular system (the heart and blood vessels) and also the immune system and inflammation. The receptor for CGRP is of special scientific interest as it involves a GPCR called CLR and also a second protein called RAMP1. RAMP1 is a member of a protein family that modulates a number of GPCRs of which the best characterised is CLR. CGRP is also likely to be important both in cardiovascular disorders and any disease that involves inflammation. The peptide is a major cause of migraine and drugs which block CGRP receptors have shown great promise in clinical trials; however, so far it has not been possible to use these clinically because of toxicity problems. Thus, there is an urgent need to develop new drugs that could act on CGRP receptors. The CGRP receptor is made up of two parts. A portion called the transmembrane domain is found in the membranes of cells. This is connected to the extracellular domain, which is on the outside of cells. CGRP interacts with both parts of this structure and causes the transmembrane domain to change shape. This causes the receptor to interact with other proteins, leading to cell activation. We have a crystal structure of the part of the CGRP receptor that is on the outside of cells. Unfortunately, we do not know how CGRP binds to this, nor do we know how it binds to the transmembrane domain. This severely limits our understanding of the receptor and our ability to design drugs that could target it. We have previously used experimental data from a technique known as site-directed mutagenesis to construct a computer model of the transmembrane domain of the CGRP receptor. This transmembrane domain is very similar to the transmembrane domains of two family-B GPCRs which were crystallised after our computer model was produced. This gives us confidence that our approach of combining experimental and computational methods is valuable. In this project, we intend to extend the approach to study how CGRP binds to both domains of the receptor and how this causes the receptor to become activated. We will use mutagenesis and also methods where we physically cross-link CGRP to the receptor to identify contact points. We will then use these to construct computational models, which we can refine through further experimentation. Using a computer, we can predict how the receptor shape will change when CGRP binds to it, so identifying the mechanism for receptor activation. This knowledge will be benefitial in the design of new drugs which can either block the receptor or promote its activation.