Huang Y, Wang JJ, Ghosh S, Liu JL. Critical roles of CTP synthase N-terminal in cytoophidium assembly.
Exp Cell Res 2017;
354:122-133. [PMID:
28342900 PMCID:
PMC5405848 DOI:
10.1016/j.yexcr.2017.03.042]
[Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Revised: 03/18/2017] [Accepted: 03/20/2017] [Indexed: 01/27/2023]
Abstract
Several metabolic enzymes assemble into distinct intracellular structures in prokaryotes and eukaryotes suggesting an important functional role in cell physiology. The CTP-generating enzyme CTP synthase forms long filamentous structures termed cytoophidia in bacteria, yeast, fruit flies and human cells independent of its catalytic activity. However, the amino acid determinants for protein-protein interaction necessary for polymerisation remained unknown. In this study, we systematically analysed the role of the conserved N-terminal of Drosophila CTP synthase in cytoophidium assembly. Our mutational analyses identified three key amino acid residues within this region that play an instructive role in organisation of CTP synthase into a filamentous structure. Co-transfection assays demonstrated formation of heteromeric CTP synthase filaments which is disrupted by protein carrying a mutated N-terminal alanine residue thus revealing a dominant-negative activity. Interestingly, the dominant-negative activity is supressed by the CTP synthase inhibitor DON. Furthermore, we found that the amino acids at the corresponding position in the human protein exhibit similar properties suggesting conservation of their function through evolution. Our data suggest that cytoophidium assembly is a multi-step process involving N-terminal-dependent sequential interactions between correctly folded structural units and provide insights into the assembly of these enigmatic structures.
CTP synthase mutational analyses reveal N-terminal amino acids that regulate filament self-assembly.
Amino acid 20 of CTP synthase plays key role in protein interactions necessary for polymerisation.
The dominant-negative activity is supressed by CTP synthase inhibitor DON.
The functional properties of the amino acids are conserved in Drosophila and human CTP synthases.
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