1SVK

Structure of the K180P mutant of Gi alpha subunit bound to AlF4 and GDP

Summary for 1SVK

• Entry DOI: 10.2210/pdb1svk/pdb
• Related: 1BOF 1GFI
• Descriptor: Guanine nucleotide-binding protein G(i), alpha-1 subunit, MAGNESIUM ION, TETRAFLUOROALUMINATE ION, ... (5 entities in total)
• Functional Keywords: gi alpha subunit, k180p mutation, active form, hydrolase, signaling protein
• Biological source: Rattus norvegicus (Norway rat)
• Cellular location: Nucleus: P10824
• Total number of polymer chains: 1
• Total formula weight: 40806.25

Authors

Thomas, C.J.,Du, X.,Li, P.,Wang, Y.,Ross, E.M.,Sprang, S.R. (deposition date: 2004-03-29, release date: 2004-06-01, Last modification date: 2023-08-23)

Primary citation

Thomas, C.J.,Du, X.,Li, P.,Wang, Y.,Ross, E.M.,Sprang, S.R.
Uncoupling conformational change from GTP hydrolysis in a heterotrimeric G protein {alpha}-subunit.
Proc.Natl.Acad.Sci.USA, 101:7560-7565, 2004

PubMed Abstract: Heterotrimeric G protein alpha (G alpha) subunits possess intrinsic GTPase activity that leads to functional deactivation with a rate constant of approximately 2 min(-1) at 30 degrees C. GTP hydrolysis causes conformational changes in three regions of G alpha, including Switch I and Switch II. Mutation of G202-->A in Switch II of G alpha(i1) accelerates the rates of both GTP hydrolysis and conformational change, which is measured by the loss of fluorescence from Trp-211 in Switch II. Mutation of K180-->P in Switch I increases the rate of conformational change but decreases the GTPase rate, which causes transient but substantial accumulation of a low-fluorescence G alpha(i1).GTP species. Isothermal titration calorimetric analysis of the binding of (G202A)G alpha(i1) and (K180P)G alpha(i1) to the GTPase-activating protein RGS4 indicates that the G202A mutation stabilizes the pretransition state-like conformation of G alpha(i1) that is mimicked by the complex of G alpha(i1) with GDP and magnesium fluoroaluminate, whereas the K180P mutation destabilizes this state. The crystal structures of (K180P)G alpha(i1) bound to a slowly hydrolyzable GTP analog, and the GDP.magnesium fluoroaluminate complex provide evidence that the Mg(2+) binding site is destabilized and that Switch I is torsionally restrained by the K180P mutation. The data are consistent with a catalytic mechanism for G alpha in which major conformational transitions in Switch I and Switch II are obligate events that precede the bond-breaking step in GTP hydrolysis. In (K180P)G alpha(i1), the two events are decoupled kinetically, whereas in the native protein they are concerted.

PubMed: 15128951
DOI: 10.1073/pnas.0304091101

Experimental method

X-RAY DIFFRACTION (2 Å)