title: pH-triggered disassembly in a caged protein complex.
abstract: Self-assembling protein cage structures have many potential applications in nanotechnology, one of which is therapeutic delivery. For intracellular targeting, pH-controlled disassembly of virus-like particles and release of their molecular cargo is particularly strategic. We investigated the potential of using histidines for introducing pH-dependent disassembly in the E2 subunit of pyruvate dehydrogenase. Two subunit interfaces likely to disrupt stability, an intratrimer interface (the N-terminus) and an intertrimer interface (methionine-425), were redesigned. Our results show that changing the identity of the putative anchor site 425 to histidine does not decrease stability. In contrast, engineering non-native pH-dependent behavior and modulating the transition pH at which disassembly occurs can be accomplished by mutagenesis of the N-terminus and by ionic strength changes. The observed pH-triggered disassembly is due to electrostatic repulsions generated by histidine protonation. These results suggest that altering the degree of electrostatic repulsion at subunit interfaces could be a generally applicable strategy for designing pH-triggered assembly in protein macromolecular structures.
authors.affiliation: Department of Chemical Engineering and Materials Science, University of California, Irvine, California 92697-2575, USA.
authors.forename: Mercè
authors.initials: M
authors.lastname: Dalmau
authors.forename: Sierin
authors.initials: S
authors.lastname: Lim
authors.forename: Szu-Wen
authors.initials: SW
authors.lastname: Wang
mesh_terms: D051047:Dihydrolipoyllysine-Residue Acetyltransferase / Q000737:chemistry* / Q000235:genetics; D004795:Enzyme Stability; D001411:Geobacillus stearothermophilus / Q000201:enzymology; D006639:Histidine / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D053758:Nanoparticles / Q000737:chemistry*; D011487:Protein Conformation
chemical_list: D006639:Histidine; D051047:Dihydrolipoyllysine-Residue Acetyltransferase