| Autor: |
Sumikawa M; Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan., Abe-Yoshizumi R; Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan., Uchihashi T; Department of Physics, Nagoya University, Nagoya 464-8602, Japan., Kandori H; Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan.; OptoBioTechnology Research Center, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan. |
| Jazyk: |
angličtina |
| Zdroj: |
Biochemistry [Biochemistry] 2022 Sep 20; Vol. 61 (18), pp. 1936-1944. Date of Electronic Publication: 2022 Aug 25. |
| DOI: |
10.1021/acs.biochem.2c00328 |
| Abstrakt: |
Proteorhodopsin (PR) is a light-driven proton pump found in marine bacteria, and thousands of PRs are classified as blue-absorbing PRs (BPR; λ max ∼ 490 nm) and green-absorbing PRs (GPR; λ max ∼ 525 nm). We previously converted BPR into GPR using an anomalous pH effect, which was achieved by an irreversible process at around pH 2. Recent size-exclusion chromatography (SEC) and atomic force microscopy (AFM) analyses of BPR from Vibrio califitulae (VcBPR) revealed the anomalous pH effect owing to the irreversible transition from pentamer to monomer. Different p K a values of the Schiff base counterion between pentamer and monomer lead to different colors at the same pH. Here, we incorporate systematic mutation into VcBPR and examine the anomalous pH effect. The anomalous pH effect was observed for the mutants of key residues near the retinal chromophore such as D76N, D206N, and Q84L, indicating that the Schiff base counterions and the L/Q switch do not affect the irreversible transition from pentamer to monomer at pH ∼ 2. We then focus on the two specific interactions at the intermonomer interface in a pentamer, E29/R30/D31 and W13/H54. Single mutants such as E29Q, R30A, W13A, and H54A and the wild type (WT) exhibited an anomalous pH effect. In contrast, the anomalous pH effect was lost for E29Q/H54A, R30A/H54A, and W13A/E29Q. Size-exclusion chromatography (SEC) and atomic force microscopy (AFM) measurements showed monomer forms in the original states of the double mutants, being a clear contrast to the pentamer forms of all single mutants in the original states. It was concluded that the pentamer structure of VcBPR was stabilized by an electrostatic interaction in the E29/R30/D31 region and a hydrogen-bonding interaction in the W13/H54 region, which was disrupted at pH 2 and converted into monomers. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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