Synthesis and biochemical characterization of EGF receptor in a water-soluble membrane model system.

ErbB (Erythroblastic Leukemia Viral Oncogene Homolog) receptor tyrosine kinases are critical for tissue development and maintenance, and frequently become oncogenic when mutated or overexpressed. In vitro analysis of ErbB receptor kinases can be difficult because of their large size and poor water solubility. Here we report improved production and assembly of the correctly folded full-length EGF receptor (EGFR) into nanolipoprotein particles (NLPs). NLPs are ~10 nm in diameter discoidal cell membrane mimics composed of apolipoproteins surrounding a lipid bilayer. NLPs containing EGFR were synthesized via incubation of baculovirus-produced recombinant EGFR with apolipoprotein and phosphoplipids under conditions that favor self-assembly. The resulting EGFR-NLPs were the correct size, formed dimers and multimers, had intrinsic autophosphorylation activity, and retained the ability to interact with EGFR-targeted ligands and inhibitors consistent with previously-published in vitro binding affinities. We anticipate rapid adoption of EGFR-NLPs for structural studies of full-length receptors and drug screening, as well as for the in vitro characterization of ErbB heterodimers and disease-relevant mutants.