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1vgo

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[[Image:1vgo.gif|left|200px]]
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{{STRUCTURE_1vgo| PDB=1vgo | SCENE= }}
{{STRUCTURE_1vgo| PDB=1vgo | SCENE= }}
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'''Crystal Structure of Archaerhodopsin-2'''
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===Crystal Structure of Archaerhodopsin-2===
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==Overview==
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Archaerhodopsin-1 and -2 (aR-1 and aR-2) are light-driven proton pumps found in Halorubrum sp. aus-1 and -2, which share 55-58% sequence identity with bacteriorhodopsin (bR), a proton pump found in Halobacterium salinarum. In this study, aR-1 and aR-2 were crystallized into 3D crystals belonging to P4(3)2(1)2 (a = b = 128.1 A, c = 117.6 A) and C222(1) (a = 122.9 A, b = 139.5 A, c = 108.1 A), respectively. In both the crystals, the asymmetric unit contains two protein molecules with slightly different conformations. Each subunit is composed of seven helical segments as seen in bR but, unlike bR, aR-1 as well as aR-2 has a unique omega loop near the N terminus. It is found that the proton pathway in the extracellular half (i.e. the proton release channel) is more opened in aR-2 than in aR-1 or bR. This structural difference accounts for a large variation in the pKa of the acid purple-to-blue transition among the three proton pumps. All the aromatic residues surrounding the retinal polyene chain are conserved among the three proton pumps, confirming a previous argument that these residues are required for the stereo-specificity of the retinal isomerization. In the cytoplasmic half, the region surrounded by helices B, C and G is highly conserved, while the structural conservation is very low for residues extruded from helices E and F. Structural conservation of the hydrophobic residues located on the proton uptake pathway suggests that their precise arrangement is necessary to prevent a backward flow of proton in the presence of a large pH gradient and membrane potential. An empty cavity is commonly seen in the vicinity of Leu93 contacting the retinal C13 methyl. Existence of such a cavity is required to allow a large rotation of the side-chain of Leu93 at the early stage of the photocycle, which has been shown to accompany water translocation across the Schiff base.
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(as it appears on PubMed at http://www.pubmed.gov), where 16540121 is the PubMed ID number.
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{{ABSTRACT_PUBMED_16540121}}
==About this Structure==
==About this Structure==
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[[Category: Proton transport]]
[[Category: Proton transport]]
[[Category: Retinal-binding protein]]
[[Category: Retinal-binding protein]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Wed Jun 11 10:53:33 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 10:25:16 2008''

Revision as of 07:25, 28 July 2008

Image:1vgo.png

Template:STRUCTURE 1vgo

Crystal Structure of Archaerhodopsin-2

Template:ABSTRACT PUBMED 16540121

About this Structure

1VGO is a Single protein structure of sequence from Halobacterium sp.. Full crystallographic information is available from OCA.

Reference

Crystal structures of archaerhodopsin-1 and -2: Common structural motif in archaeal light-driven proton pumps., Enami N, Yoshimura K, Murakami M, Okumura H, Ihara K, Kouyama T, J Mol Biol. 2006 May 5;358(3):675-85. Epub 2006 Mar 3. PMID:16540121

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