1ohb

File:1ohb.jpg

spinqualitylabelsall models 1ohb, resolution 1.90Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

ACETYLGLUTAMATE KINASE FROM ESCHERICHIA COLI COMPLEXED WITH ADP AND SULPHATE

OverviewOverview

N-Acetyl-L-glutamate kinase (NAGK), the structural paradigm of the enzymes, of the amino acid kinase family, catalyzes the phosphorylation of the, gamma-COO(-) group of N-acetyl-L-glutamate (NAG) by ATP. We determine here, the crystal structures of NAGK complexes with MgADP, NAG and the, transition-state analog AlF(4)(-); with MgADP and NAG; and with ADP and, SO(4)(2-). Comparison of these structures with that of the MgAMPPNP-NAG, complex allows to delineate three successive steps during phosphoryl, transfer: at the beginning, when the attacking and leaving O atoms and the, P atom are imperfectly aligned and the distance between the attacking O, atom and the P atom is 2.8A; midway, at the bipyramidal intermediate, with, nearly perfect alignment and a distance of 2.3A; and, when the transfer is, completed. The transfer occurs in line and is strongly associative, with, Lys8 and Lys217 stabilizing the transition state and the leaving group, respectively, and with Lys61, in contrast with an earlier proposal, not, being involved. Three water molecules found in all the complexes play, together with Asp162 and the Mg, crucial structural roles. Two, glycine-rich loops (beta1-alphaA and beta2-alphaB) are also very, important, moving in the different complexes in concert with the ligands, to which they are hydrogen-bonded, either locking them in place for, reaction or stabilizing the transition state. The active site is too, narrow to accommodate the substrates without compressing the reacting, groups, and this compressive strain appears a crucial component of the, catalytic mechanism of NAGK, and possibly of other enzymes of the amino, acid kinase family such as carbamate kinase. Initial binding of the two, substrates would require a different enzyme conformation with a wider, active site, and the energy of substrate binding would be used to change, the conformation of the active center, causing substrate strain towards, the transition state.

About this StructureAbout this Structure

1OHB is a Single protein structure of sequence from Escherichia coli with SO4, ACT and ADP as ligands. Active as Acetylglutamate kinase, with EC number 2.7.2.8 Known structural/functional Site: . Full crystallographic information is available from OCA.

ReferenceReference

The course of phosphorus in the reaction of N-acetyl-L-glutamate kinase, determined from the structures of crystalline complexes, including a complex with an AlF(4)(-) transition state mimic., Gil-Ortiz F, Ramon-Maiques S, Fita I, Rubio V, J Mol Biol. 2003 Aug 1;331(1):231-44. PMID:12875848

Page seeded by OCA on Tue Dec 18 17:43:51 2007