John Engen - Faculty Profile

John R. Engen holds a joint appointment as an Associate Professor in the Department of Chemistry and Chemical Biology and a Faculty Fellow in the Barnett Institute of Chemical and Biological Analysis. Research in the laboratory centers on the use of state-of-the-art mass spectrometry (MS) to study the conformations and movements of proteins and protein machines. Mass spectrometry can be used to study protein conformation if the proteins in question are labeled with a structure-dependent labeling method such as amide hydrogen exchange (HX). Proteins contain a number of hydrogens that can exchange with hydrogen in the surrounding solvent. The most useful hydrogen to follow is the backbone amide hydrogen. If the normal H2O solvent is changed to D2O, the protein gradually becomes deuterated. Because deuterium and hydrogen differ in mass by 1 dalton, the incorporation of deuterium (aka, hydrogen exchange) into a protein can be monitored with high resolution mass spectrometry. The rate of HX depends on hydrogen bonding and solvent accessibility. Folded proteins can have amino acids with HX rates as much as 1 billion times slower than the same amino acid that is not in a folded protein. Protein folding and unfolding, whether in cells or in the test tube, represent large changes in protein structure, hydrogen bonding and solvent accessibility that can be investigated with HX MS. Smaller structural changes critical for protein function can also be probed with HX MS. Projects of current interest include: (1) the analysis of structural changes in the Src-family of tyrosine kinases during interactions with regulatory proteins; (2) the analysis of the conformational features of viral proteins that are not amenable to crystallography or NMR; (3) applications of HX MS to biopharmaceuticals.