A prototype protein nanocage minimized from carboxysomes with gated oxygen permeability

Protein nanocages (PNCs) in cells and viruses have inspired the development of self-assembling protein nanomaterials for various purposes. Despite the successful creation of artificial PNCs, the de novo design of PNCs with defined permeability remains challenging. Here, we report a prototype oxygen-impermeable PNC (OIPNC) assembled from the vertex protein of the j3-carboxysome shell, CcmL, with quantum dots as the template via interfacial engineering. The structure of the cage was solved at the atomic scale by combined solid-state NMR spectroscopy and cryoelectron microscopy, showing icosahedral assembly of CcmL pentamers with highly conserved interpentamer interfaces. Moreover, a gating mechanism was established by reversibly blocking the pores of the cage with molecular patches. Thus, the oxygen permeability, which was probed by an oxygen sensor inside the cage, can be completely controlled. The CcmL OIPNC represents a PNC platform for oxygen-sensitive or oxygen-responsive storage, catalysis, delivery, sensing, etc.

Automated summary

In this study, an oxygen-impermeable protein nanocage (OIPNC) was assembled from the vertex protein of the j3-carboxysome shell, CcmL, using quantum dots as a template via interfacial engineering. The structure of the cage was solved at the atomic scale and a gating mechanism was established to control oxygen permeability. The CcmL OIPNC represents a versatile platform for various applications.