5AX0: Crystal Structure Of The Cell-free Synthesized Membrane Protein, Acetabularia Rhodopsin I, At 1.52 Angstrom

Citation:
Abstract
Although many crystal structures of microbial rhodopsins have been solved, those with sufficient resolution to identify the functional water molecules are very limited. In this study, the Acetabularia rhodopsin I (ARI) protein derived from the marine alga A. acetabulum was synthesized on a large scale by the Escherichia coli cell-free membrane-protein production method, and crystal structures of ARI were determined at the second highest (1.52-1.80 A) resolution for a microbial rhodopsin, following bacteriorhodopsin (BR). Examinations of the photochemical properties of ARI revealed that the photocycle of ARI is slower than that of BR and that its proton-transfer reactions are different from those of BR. In the present structures, a large cavity containing numerous water molecules exists on the extracellular side of ARI, explaining the relatively low pKa of Glu206(ARI), which cannot function as an initial proton-releasing residue at any pH. An interhelical hydrogen bond exists between Leu97(ARI) and Tyr221(ARI) on the cytoplasmic side, which facilitates the slow photocycle and regulates the pKa of Asp100(ARI), a potential proton donor to the Schiff base, in the dark state.
PDB ID: 5AX0Download
MMDB ID: 132104
PDB Deposition Date: 2015/7/10
Updated in MMDB: 2015/11
Experimental Method:
x-ray diffraction
Resolution: 1.52  Å
Similar Structures:
Biological Unit for 5AX0: monomeric; determined by author and by software (PISA)
Molecular Components in 5AX0
Label Count Molecule
Protein (1 molecule)
1
Rhodopsin I
Molecule annotation
Chemicals (10 molecules)
1
1
2
3
3
2
4
1
5
1
6
2
* Click molecule labels to explore molecular sequence information.

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