pH-triggered disassembly in a caged protein complex.
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.
Dalmau
Mercè
M
Department of Chemical Engineering and Materials Science, University of California, Irvine, California 92697-2575, USA.
Lim
Sierin
S
Wang
Szu-Wen
SW
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
D006639:Histidine; D051047:Dihydrolipoyllysine-Residue Acetyltransferase