9EEK
Cryo-EM model of E. coli aspartate transcarbamoylase in the ligand-free T-state
Summary for 9EEK
| Entry DOI | 10.2210/pdb9eek/pdb |
| Related | 9EEH 9EEJ 9EEL 9EEM 9EEN 9EEO 9EEP 9EEQ 9EER 9EES 9EEU |
| EMDB information | 47956 47957 47958 47959 47960 47961 47963 47964 47965 47966 |
| Descriptor | Aspartate carbamoyltransferase regulatory chain, Aspartate carbamoyltransferase, ZINC ION (3 entities in total) |
| Functional Keywords | complex, allostery, atcase, t-state, cytosolic protein |
| Biological source | Escherichia coli More |
| Total number of polymer chains | 12 |
| Total formula weight | 309276.83 |
| Authors | |
| Primary citation | Miller, R.C.,Patterson, M.G.,Bhatt, N.,Pei, X.,Ando, N. Cooperativity in E. coli aspartate transcarbamoylase is tuned by allosteric breathing. Nat Commun, 2026 Cited by PubMed Abstract: Aspartate transcarbamoylase (ATCase) from Escherichia coli catalyzes a key step in pyrimidine nucleotide biosynthesis and has long served as a model for allosteric regulation. Despite decades of study, how nucleotide binding at distant regulatory sites controls cooperativity between active sites remained unresolved. Here we show that ATCase does not simply interconvert between two conformations, as traditionally depicted, but instead samples a continuum of conformations that tune enzyme cooperativity. Using complementary cryo-electron microscopy, small-angle X-ray scattering, and crystallography under conditions that ensure full assembly of the allosteric sites, we show that ATCase behaves like a flexible balloon whose global "breathing" motions directly regulate activity: compression enforces high cooperativity, inhibiting the enzyme, whereas expansion relieves this cooperativity and activates the enzyme. We further show that all four ribonucleoside triphosphates act in symmetric pairs to tune this motion, with the pyrimidines CTP and UTP compressing the enzyme to limit further pyrimidine production, and the purines ATP and GTP expanding it to balance pyrimidine and purine pools. Together, these findings uncover a dynamic breathing mechanism for long-range allosteric communication in ATCase. PubMed: 41862478DOI: 10.1038/s41467-026-70909-y PDB entries with the same primary citation |
| Experimental method | ELECTRON MICROSCOPY (2.62 Å) |
Structure validation
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