1GFI

STRUCTURES OF ACTIVE CONFORMATIONS OF GI ALPHA 1 AND THE MECHANISM OF GTP HYDROLYSIS

Summary for 1GFI

• Entry DOI: 10.2210/pdb1gfi/pdb
• Descriptor: GUANINE NUCLEOTIDE-BINDING PROTEIN G, MAGNESIUM ION, TETRAFLUOROALUMINATE ION, ... (5 entities in total)
• Functional Keywords: signal transduction protein
• Biological source: Rattus norvegicus (Norway rat)
• Cellular location: Nucleus: P10824
• Total number of polymer chains: 1
• Total formula weight: 40838.32

Authors

Coleman, D.E.,Berghuis, A.M.,Sprang, S.R. (deposition date: 1994-11-11, release date: 1995-03-31, Last modification date: 2024-02-07)

Primary citation

Coleman, D.E.,Berghuis, A.M.,Lee, E.,Linder, M.E.,Gilman, A.G.,Sprang, S.R.
Structures of active conformations of Gi alpha 1 and the mechanism of GTP hydrolysis.
Science, 265:1405-1412, 1994

PubMed Abstract: Mechanisms of guanosine triphosphate (GTP) hydrolysis by members of the G protein alpha subunit-p21ras superfamily of guanosine triphosphatases have been studied extensively but have not been well understood. High-resolution x-ray structures of the GTP gamma S and GDP.AlF4- complexes formed by the G protein Gi alpha 1 demonstrate specific roles in transition-state stabilization for two highly conserved residues. Glutamine204 (Gln61 in p21ras) stabilizes and orients the hydrolytic water in the trigonal-bipyramidal transition state. Arginine 178 stabilizes the negative charge at the equatorial oxygen atoms of the pentacoordinate phosphate intermediate. Conserved only in the G alpha family, this residue may account for the higher hydrolytic rate of G alpha proteins relative to those of the p21ras family members. The fold of Gi alpha 1 differs from that of the homologous Gt alpha subunit in the conformation of a helix-loop sequence located in the alpha-helical domain that is characteristic of these proteins; this site may participate in effector binding. The amino-terminal 33 residues are disordered in GTP gamma S-Gi alpha 1, suggesting a mechanism that may promote release of the beta gamma subunit complex when the alpha subunit is activated by GTP.

PubMed: 8073283

Experimental method

X-RAY DIFFRACTION (2.2 Å)