2i20
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Bacteriorhodopsin/lipid complex, M state of D96A mutant
OverviewOverview
The X-ray diffraction structure of the non-illuminated D96A, bacteriorhodopsin mutant reveals structural changes as far away as 15 A, from residue 96, at the retinal, Trp-182, Ala-215, and waters 501, 402, and 401. The Asp-to-Ala side-chain replacement breaks its hydrogen bond, with Thr-46, and the resulting separation of the cytoplasmic ends of, helices B and C is communicated to the retinal region through a chain of, covalent and hydrogen bonds. The unexpected long-range consequences of the, D96A mutation include breaking the hydrogen bond between O of Ala-215 and, water 501 and the formation of a new hydrogen bond between water molecules, 401 and 402 in the extracellular region. Because in the T46V mutant a new, water molecule appears at Asp-96 and its hydrogen-bond to Ile-45 replaces, Thr-46 as its link to helix B, the separation of helices B and C is, smaller than that in D96A, and there are no atomic displacements elsewhere, in the protein. Propagation of conformational changes along the chain, between the retinal and Thr-46 had been observed earlier in the crystal, structures of the D96N and E204Q mutants but in the trapped M state., Consistent with the perturbation of the retinal region in D96A, little, change of the Thr-46 region occurs between the non-illuminated and M, states of this mutant. It appears that a local perturbation can propagate, along a track in both directions between the retinal and the Asp-96/Thr-46, pair, either from photoisomerization of the retinal in the wild-type, protein in one case or from the D96A mutation in the other.
About this StructureAbout this Structure
2I20 is a Single protein structure of sequence from Halobacterium salinarum with RET, LI1 and SQU as ligands. Full crystallographic information is available from OCA.
ReferenceReference
Propagating structural perturbation inside bacteriorhodopsin: crystal structures of the M state and the D96A and T46V mutants., Lanyi JK, Schobert B, Biochemistry. 2006 Oct 3;45(39):12003-10. PMID:17002299
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