1BOF

GI-ALPHA-1 BOUND TO GDP AND MAGNESIUM

Summary for 1BOF

• Entry DOI: 10.2210/pdb1bof/pdb
• Descriptor: GI ALPHA 1, SULFATE ION, MAGNESIUM ION, ... (5 entities in total)
• Functional Keywords: signal transduction protein, gtp-ase, g protein
• Biological source: Rattus norvegicus (Norway rat)
• Cellular location: Nucleus: P10824
• Total number of polymer chains: 1
• Total formula weight: 40927.47

Authors

Coleman, D.E.,Sprang, S.R. (deposition date: 1998-08-04, release date: 1999-01-06, Last modification date: 2024-05-22)

Primary citation

Coleman, D.E.,Sprang, S.R.
Crystal structures of the G protein Gi alpha 1 complexed with GDP and Mg2+: a crystallographic titration experiment.
Biochemistry, 37:14376-14385, 1998

PubMed Abstract: The effect of Mg2+ binding on the conformation of the inactive GDP-bound complex of the heterotrimeric G protein alpha subunit Gi alpha 1 has been investigated by X-ray crystallography. Crystal structures of the Gi alpha 1.GDP complex were determined after titration with 5, 10, 100, and 200 mM Mg2+. Comparison of these structures with that of the Mg2+-free complex revealed Mg2+ bound at the same site as observed in the structure of the active, Gi alpha 1. GTP gamma S.Mg2+-bound complex of Gi alpha 1, with a similar coordination scheme except for the substitution of a water molecule for an oxygen ligand of the gamma-phosphate of Gi alpha 1.GTP gamma S. Mg2+. In contrast to the GDP.Mg2+ complex of Gt alpha and of other G proteins, switch I residues of Gi alpha 1 participate in Mg2+ binding and undergo conformational changes as a consequence of Mg2+ binding. Partial order is induced in switch II, which is disordered in the Mg2+-free complex, but no order is observed in the switch III region. This contrasts with the GDP.Mg2+ complex of Gt alpha in which both switch II and III switch are ordered. Mg2+ binding also induces binding of an SO42- molecule to the active site in a manner which may mimic a Gi alpha 1.GDP.PO42-.Mg2+ product complex. Implications of these findings are discussed.

PubMed: 9772163
DOI: 10.1021/bi9810306

Experimental method

X-RAY DIFFRACTION (2.2 Å)