pH-triggered disassembly in a caged protein complex
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Updated: Jun 19, 2026

Using In Vitro Fluorescence Resonance Energy Transfer to Study the Dynamics Of Protein Complexes at a Millisecond Time Scale
Published on: March 14, 2019
Mercè Dalmau1, Sierin Lim, Szu-Wen Wang
1Department of Chemical Engineering and Materials Science, University of California, Irvine, California 92697-2575, USA.
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.
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