Domain motions of glucosamine-6P synthase: Comparison of the anisotropic displacements in the crystals and the catalytic hinge-bending rotation
Résumé
Glucosamine-6-phosphate synthase channels ammonia over 18 Å from glutamine at the glutaminase site to fructose-6P at the synthase site. We have modeled the anisotropic displacements of the glutaminase and synthase domains from the two crystallized states, the enzyme in complex with fructose-6P or in complex with glucose-6P and a glutamine affinity analog, using TLS (rigid-body motion in terms of translation, libration, and screw motions) refinement implemented in REFMAC. The domains displacements in the crystal lattices are compared to the movement of the glutaminase domain relative to the synthase domain that occurs during the catalytic cycle upon glutamine binding, which was visualized by comparing the two structures. This movement was analyzed by the program DYNDOM as a 22.8°r otation around an effective hinge axis running approximately parallel to helix 300-317 of the synthase domain, the glutaminase loop that covers the glutaminase site upon glutamine binding acting as the mechanical hinge.
Mots clés
dynamic domains
hinge-bending domain motion
domain movement
translation-librationscrew refinement
anisotropic temperature factor
dynamic domains
GlmS
glucosamine-6-phosphate synthase
Fru6P
D-fructose-6-phosphate
Glc6P
D-glucose-6-phosphate
DON
6-diazo-5-oxo-L-nor-leucine
TLS
translation-librationscrew
NCS
non crystallographic symmetry
rmsd
root mean square deviation dynamic domains
translationlibration-screw refinement
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