Optimizing Nanodiscs for Membrane Proteins and Mapping a Translation Initiation Complex

Abstract

Nanodiscs have been an excellent tool for encouraging biochemists and structural biologists to study membrane proteins. They are composed of a discoidal lipid bilayer and two copies of a membrane scaffold protein (MSP). It is possible to reconstitute an integral membrane protein into them—the enhanced stability and ability to provide a lipid environment allows for sophisticated biochemical and biophysical study. In the first part of this thesis, we present a method to improve nanodiscs by covalently circularizing MSP prior to nanodisc assembly. We highlight the enhanced stability of the particles, and show that they assemble more uniformly sized particles. The benefits of this are illustrated in applications for nuclear magnetic resonance (NMR) spectroscopy on voltage dependent anion channel-1 (VDAC-1). In the second part of this thesis, we explore the complex formed between eukaryotic initiation factor 4A (eIF4A) and the HEAT2 domain of eukaryotic initiation factor 4G (eIF4G-HEAT2). Through chemical modification of the eIF4G-HEAT2 domain, we use paramagnetic lanthanides to monitor psuedocontact shifts (PCSs) in the NMR spectra for both sides of the complex. We present the shifts observed and map them to the complex. In the end, we illustrate that this method could be viable for determining a solution structure for a large, dynamic protein complex.