PDBsum entry 1f4z

Proton transport, membrane protein

PDB id: 1f4z

Contents

Protein chain

222 a.a. *

Ligands

LI1 ×13

SQU

RET

Waters ×25

* Residue conservation analysis

PDB id:

1f4z

Name:

Proton transport, membrane protein

Title:

Bacteriorhodopsin-m photointermediate state of the e204q mutant at 1.8 angstrom resolution

Structure:

Bacteriorhodopsin. Chain: a. Synonym: br. Engineered: yes. Mutation: yes

Source:

Halobacterium salinarum. Organism_taxid: 2242. Expressed in: halobacterium salinarum. Expression_system_taxid: 2242

Biol. unit:

Trimer (from PDB file)

Resolution:

1.80Å R-factor: 0.142 R-free: 0.203

Authors:

H.Luecke,B.Schobert,J.P.Cartailler,H.T.Richter,A.Rosengarth, R.Needleman,J.K.Lanyi

Key ref:

H.Luecke et al. (2000). Coupling photoisomerization of retinal to directional transport in bacteriorhodopsin. J Mol Biol, 300, 1237-1255. PubMed id: 10903866 DOI: 10.1006/jmbi.2000.3884

Date:

10-Jun-00 Release date: 09-Aug-00

Protein chain

P02945  (BACR_HALSA) -  Bacteriorhodopsin from Halobacterium salinarum (strain ATCC 700922 / JCM 11081 / NRC-1)

Seq: 262 a.a.

Struc: 222 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

DOI no: 10.1006/jmbi.2000.3884

J Mol Biol 300:1237-1255 (2000)

PubMed id: 10903866

Coupling photoisomerization of retinal to directional transport in bacteriorhodopsin.

H.Luecke, B.Schobert, J.P.Cartailler, H.T.Richter, A.Rosengarth, R.Needleman, J.K.Lanyi.

ABSTRACT

In order to understand how isomerization of the retinal drives unidirectional transmembrane ion transport in bacteriorhodopsin, we determined the atomic structures of the BR state and M photointermediate of the E204Q mutant, to 1.7 and 1.8 A resolution, respectively. Comparison of this M, in which proton release to the extracellular surface is blocked, with the previously determined M in the D96N mutant indicates that the changes in the extracellular region are initiated by changes in the electrostatic interactions of the retinal Schiff base with Asp85 and Asp212, but those on the cytoplasmic side originate from steric conflict of the 13-methyl retinal group with Trp182 and distortion of the pi-bulge of helix G. The structural changes suggest that protonation of Asp85 initiates a cascade of atomic displacements in the extracellular region that cause release of a proton to the surface. The progressive relaxation of the strained 13-cis retinal chain with deprotonated Schiff base, in turn, initiates atomic displacements in the cytoplasmic region that cause the intercalation of a hydrogen-bonded water molecule between Thr46 and Asp96. This accounts for the lowering of the pK(a) of Asp96, which then reprotonates the Schiff base via a newly formed chain of water molecules that is extending toward the Schiff base.

Selected figure(s)

Figure 2.
Figure 2. 2F[o] -F[c] density maps of BR and M states of E204Q, contoured at 1s, of the region of the retinal, Lys216, Asp85, Trp182, and water molecules 401, 402, 501, 502, and 503. (a) BR state; (b) M state.

Figure 7.
Figure 7. Models of BR, earlier M (from E204Q) and late M (from D96N) of the region that includes the retinal, Trp182, Thr178, Lys216, Ala215, Thr46, Asp96, and water molecules 501, 502, 503 and 504, shown in stereo view. Color code for the BR, and the earlier and late M states, as in Figure 3. (a) Comparison of the BR and M states of the E204Q mutant. (b) Comparison of the BR and M states of the D96N mutant.

The above figures are reprinted by permission from Elsevier: J Mol Biol (2000, 300, 1237-1255) copyright 2000.

Figures were selected by an automated process.