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1bof
From Proteopedia
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Revision as of 13:50, 5 November 2007
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GI-ALPHA-1 BOUND TO GDP AND MAGNESIUM
Overview
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.
About this Structure
1BOF is a Single protein structure of sequence from Rattus norvegicus with SO4, MG and GDP as ligands. Structure known Active Site: MG. Full crystallographic information is available from OCA.
Reference
Crystal structures of the G protein Gi alpha 1 complexed with GDP and Mg2+: a crystallographic titration experiment., Coleman DE, Sprang SR, Biochemistry. 1998 Oct 13;37(41):14376-85. PMID:9772163
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