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Titolo:
The allosteric transition of glucosamine-6-phosphate deaminase: The structure of the T state at 2.3 angstrom resolution
Autore:
Horjales, E; Altamirano, MM; Calcagno, ML; Garratt, RC; Oliva, G;
Indirizzi:
UnivoNacl Autonoma Mexico, Inst Biotecnol, Cuernavaca 62271, Morelos, Mexic Univ Nacl Autonoma Mexico Cuernavaca Morelos Mexico 62271 Morelos, Mexic Univxicol Autonoma Mexico, Fac Med, Dept Bioquim, Mexico City 04510, DF, Me Univ Nacl Autonoma Mexico Mexico City DF Mexico 04510 City 04510, DF, Me Univ Sao Paulo, Inst Fis Sao Carlos, BR-13590970 Sao Carlos, SP, Brazil Univ Sao Paulo Sao Carlos SP Brazil BR-13590970 BC Sao Carlos, SP, Brazil
Titolo Testata:
STRUCTURE WITH FOLDING & DESIGN
fascicolo: 5, volume: 7, anno: 1999,
pagine: 527 - 537
SICI:
0969-2126(199905)7:5<527:TATOGD>2.0.ZU;2-4
Fonte:
ISI
Lingua:
ENG
Soggetto:
ESCHERICHIA-COLI; ENTROPY-DRIVEN; MECHANISM; HEMOGLOBIN; ISOMERASE; ENZYMES; SITE;
Keywords:
aldose-ketose isomerase; allosteric enzyme; allosteric transition; entropic effects;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
31
Recensione:
Indirizzi per estratti:
Indirizzo: Horjales, E Univelos, Autonoma Mexico, Inst Biotecnol, POB 510-3, Cuernavaca 62271, Mor Univ Nacl Autonoma Mexico POB 510-3 Cuernavaca Morelos Mexico62271
Citazione:
E. Horjales et al., "The allosteric transition of glucosamine-6-phosphate deaminase: The structure of the T state at 2.3 angstrom resolution", STRUCT F D, 7(5), 1999, pp. 527-537

Abstract

Background: The allosteric hexameric enzyme glucosamine-6-phosphate deaminase from Escherichia coli catalyses the regulatory step of N-acetylglucosamine catabolism, which consists of the isomerisation and deamination of glucosamine 6-phosphate (GlcN6P) to form fructose 6-phosphate (Fru6P) and ammonia. The reversibility of the catalysis and its rapid-equilibrium random kinetic mechanism, among other properties, make this enzyme a good model for studying allosteric processes. Results: Here we present the structure of P6(3)22 crystals, obtained in sodium acetate, of GlcN6P deaminase in its ligand-free T state. These crystals are very sensitive to X-ray radiation and have a high (78%) solvent content. The active-site lid (residues 162-185) is highly disordered in the T conformer; this may contribute significantly to the free-energy change of thewhole allosteric transition, Comparison of the structure with the crystallographic coordinates of the R conformer (Brookhaven Protein Data Bank entry1 dea) allows us to describe the geometrical changes associated with the allosteric transition as the movement of two rigid entities within each monomer. The active site, located in a deep cleft between these two rigid entities, presents a more open geometry in the T conformer than in the R conformer. Conclusions: The differences in active-site geometry are related to alterations in the substrate-binding properties associated with the allosteric transition. The rigid nature of the two mobile structural units of each monomer seems to be essential in order to explain the observed kinetics of the deaminase hexamer. The triggers for both the homotropic and heterotropic allosteric transitions are discussed and particular residues are assigned to these functions. A structural basis for an entropic term in the allosteric transition is an interesting new feature that emerges from this study.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 19/09/20 alle ore 11:38:56