Assembly status transition offers an avenue for activity modulation of a supramolecular enzyme.

Weiya Xu,Shuwei Yu,Yao Chen,Chengdong Huang,Xiaodong Ye,Qiong Xing,Kang Ni,Guangbiao She,Jian Zhao

doi:10.7554/elife.72535

Abstract

Nature has evolved many supramolecular proteins assembled in certain, sometimes even seemingly oversophisticated, morphological manners. The rationale behind such evolutionary efforts is often poorly understood. Here, we provide atomic-resolution insights into how the dynamic building of a structurally complex enzyme with higher order symmetry offers amenability to intricate regulation. We have established the functional coupling between enzymatic activity and protein morphological states of glutamine synthetase (GS), an old multi-subunit enzyme essential for cellular nitrogen metabolism. Cryo-EM structure determination of GS in both the catalytically active and inactive assembly states allows us to reveal an unanticipated self-assembly-induced disorder-order transition paradigm, in which the remote interactions between two subcomplex entities significantly rigidify the otherwise structurally fluctuating active sites, thereby regulating activity. We further show in vivo evidences that how the enzyme morphology transitions could be modulated by cellular factors on demand. Collectively, our data present an example of how assembly status transition offers an avenue for activity modulation, and sharpens our mechanistic understanding of the complex functional and regulatory properties of supramolecular enzymes.

Highlights

Recent studies have evidenced that only a small portion of proteins function in isolation in cells, whereas the majority is assembled into complexes through protein-protein interactions with identical or different protein subunit(s) (Marsh et al, 2013)
We examined the in vivo interactions between Cs14-3-3-1a and CsGSIb using the bimolecular fluorescence complementation (BiFC) technique, which is based on complementation between two non-fluorescent fragments of a fluorescent protein when they are brought together by interactions between proteins fused to each fragment Kerppola, 2006
Comparing to the oligomer assembled in relatively simple cyclic symmetry that contains only interfaces of subunits related by the rotational symmetry, protein complexes organized in dihedral symmetry, an extra step of assembly during evolution, possess interfaces that are related by both the rotational symmetry and the perpendicular twofold axes

Summary

Introduction

Recent studies have evidenced that only a small portion of proteins function in isolation in cells, whereas the majority is assembled into complexes through protein-protein interactions with identical or different protein subunit(s) (Marsh et al, 2013). The rationale behind such an evolutionary selection has been the subject of considerable speculation; proposals for the advantages associated with a multimeric-u nits complex instead of a long single polypeptide chain include better error control in synthesis, greater coding and folding efficiency, and possibility of allosteric regulation (Goodsell and Olson, 2000).

Results

Discussion

Materials and methods

Funding Funder