In situ monitoring of protein transfer into nanoscale channels

Abstract

Protein transfer into nanoscale compartments is critical for many cellular/life processes, yet there are few reports on how compartment properties impact the protein orientation during a transfer. Such a knowledge gap limits a deeper understanding of the protein transfer mechanism, which could be bridged using nanoporous materials. Here, we use a mesoporous silica, a covalent organic framework, and a metal-organic framework with charged, hydrophobic, and neutral surfaces, respectively, to elucidate the impact of channel properties on the transfer of a model protein, lysozyme. Using site-directed spin labeling and time-resolved electron paramagnetic resonance spectroscopy, we reveal that the transfer can be a multi-step process depending on channel properties and depict the relative orientation changes of lysozyme upon transfer into each channel. To the best of our knowledge, this is the first structural insight into protein orientation upon transfer into different compartments, meaningful for the rational design of synthetic materials to host enzymes or mimic the cellular compartments. Protein transfer into nanoscale channels differing in hydrophobicity is demonstrated Multi-step protein transfer is observed for charged and hydrophobic channels Protein changes its orientation depending on the channel surface properties Time-resolved EPR spectroscopy can reveal residue-level details of protein transfer Pan et al. report the orientation changes of a model protein upon transfer into three nanoscale channels that differ in surface hydrophobicity (but a similar diameter). The findings may be useful for guiding the rational design of synthetic materials to host enzymes and/or mimic the cellular compartments.