Mechanisms of co-translational assembly of multi-protein complexes

Introduction

Most proteins function within larger complexes. How these intricate structures are correctly formed is poorly understood, yet critical to all cellular processes and pathological conditions. Recent breakthroughs suggest that multi-protein complexes form co-translationally, by super-assemblies of multiple ribosomes and other cofactors that are coordinated in time and space. This striking notion contrasts starkly with textbook models and is key to the possibilities and failures of complex formation.

Technical Limitations

However, owing to technical limitations, the mechanisms and scope of actively coordinated protein assembly are poorly understood. Elucidating how these large and transient co-translational formations produce protein complexes throughout the genome is a next-level challenge that cannot be addressed by a single discipline.

Proposed Approaches

We propose a unique merging of cutting-edge approaches:

1. Ribosomal profiling to detect interactions between ribosomes engaged in assembly and cofactors genome-wide.
2. Single-molecule force spectroscopy and super-resolution imaging to reveal ribosome movements and nascent chain assembly.
3. Cryo-EM and tomography to elucidate the structural basis of ribosome interactions that enable direct assembly.

Program Objectives

Our program addresses:

1. The coordination of multiple ribosomes in time and space.
2. The folding and assembly of nascent chains, and guidance by chaperones and novel cofactors.
3. The major protein complex classes of homo-dimers, higher-order oligomers, hetero-dimers, and complexes formed at membranes.

Expected Impact

This ambitious program will provide insight of unprecedented detail and scope, spanning from the cellular to the atomic level, from in vivo to in vitro, from genome-wide patterns to molecular mechanisms, and from bacteria to human cells. It will impact a vast spectrum of protein complexes, reveal unknown layers of control in protein biogenesis, with implications for ribosome quality control, artificial protein design, and mechanisms of disease.