Structural basis of rhodopsin/G protein coupling: biochemical activity of peptide complexes, photo cross-linking, and mass spectrometric analysis

Physiological and sensory mechanisms are primarily controlled by membrane impermeant signals—which are usually detected by membrane-spanning receptor proteins that ultimately trigger intracellular responses. Similarly, development and repair in multi-cellular organisms are controlled by specific adhesion mechanisms that recognize macromolecular binding sites outside cells and control cytoplasmic responses. Understanding of signaling and adhesion mechanisms could be greatly advanced if the structures of the membrane-spanning receptor proteins and their non-covalent interaction partners could be determined at atomic resolution—but these structures can not typically be deduced by x-ray crystallography or NMR. Mass spectrometry is able to mass analyze high molecular weight species, however, non-covalent protein-ligand or protein-protein interactions are disrupted by the non-aqueous conditions used in conventional mass spectrometry. This thesis describes new mass spectrometric methodologies to analyze proteins directly from aqueous solutions, which is an important first step in mass spectrometry of non-covalent protein-ligand complexes. Insight is gained into fundamental mechanisms of laser desorption ionization mass spectrometry from aqueous solutions. This thesis also describes biochemical and mass spectrometric methods to identify non-covalen