Native protein nanolithography that can write, read and erase.

The development of systematic approaches to explore protein-protein interactions and dynamic protein networks is at the forefront of biological sciences. Nanopatterned protein arrays offer significant advantages for sensing applications, including short diffusion times, parallel detection of multiple targets and the requirement for only tiny amounts of sample. Atomic force microscopy (AFM) based techniques have successfully demonstrated patterning of molecules, including stable proteins, with submicrometre resolution.

Proteasome assembly triggers a switch required for active-site maturation.

The processing of propeptides and the maturation of 20S proteasomes require the association of beta rings from two half proteasomes. We propose an assembly-dependent activation model in which interactions between helix (H3 and H4) residues of the opposing half proteasomes are prerequisite for appropriate positioning of the S2-S3 loop; such positioning enables correct coordination of the active-site residue needed for propeptide cleavage. Mutations of H3 or H4 residues that participate in the association of two half proteasomes inhibit activation and prevent, in nearly all cases, the formation of full proteasomes.