5u03
Cryo-EM structure of the human CTP synthase filament
Structural highlights
DiseasePYRG1_HUMAN The disease is caused by mutations affecting the gene represented in this entry. A unique and recessive G to C mutation probably affecting a splice donor site at the junction of intron 17-18 and exon 18 has been identified in all patients. It results in expression of an abnormal transcript lacking exon 18 and a complete loss of the expression of the protein.[1] FunctionPYRG1_HUMAN This enzyme is involved in the de novo synthesis of CTP, a precursor of DNA, RNA and phospholipids. Catalyzes the ATP-dependent amination of UTP to CTP with either L-glutamine or ammonia as a source of nitrogen. This enzyme and its product, CTP, play a crucial role in the proliferation of activated lymphocytes and therefore in immunity.[2] [3] Publication Abstract from PubMedThe universally conserved enzyme CTP synthase (CTPS) forms filaments in bacteria and eukaryotes. In bacteria, polymerization inhibits CTPS activity and is required for nucleotide homeostasis. Here we show that for human CTPS, polymerization increases catalytic activity. The cryo-EM structures of bacterial and human CTPS filaments differ considerably in overall architecture and in the conformation of the CTPS protomer, explaining the divergent consequences of polymerization on activity. The structure of human CTPS filament, the first structure of the full-length human enzyme, reveals a novel active conformation. The filament structures elucidate allosteric mechanisms of assembly and regulation that rely on a conserved conformational equilibrium. The findings may provide a mechanism for increasing human CTPS activity in response to metabolic state and challenge the assumption that metabolic filaments are generally storage forms of inactive enzymes. Allosteric regulation of CTPS polymerization by ligands likely represents a fundamental mechanism underlying assembly of other metabolic filaments. Human CTP synthase filament structure reveals the active enzyme conformation.,Lynch EM, Hicks DR, Shepherd M, Endrizzi JA, Maker A, Hansen JM, Barry RM, Gitai Z, Baldwin EP, Kollman JM Nat Struct Mol Biol. 2017 May 1. doi: 10.1038/nsmb.3407. PMID:28459447[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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