Vibrational Study of the Inward Proton Pump Xenorhodopsin NsXeR: Switch Order Determines Vectoriality

Asido, Marvin; Boumrifak, Chokri; Weissbecker, Juliane; Bamberg, Ernst; Wachtveitl, Josef

doi:10.1016/j.jmb.2024.168447

“…S5c ). This near-UV band was previously termed as second bright state (SBS) and was shown to be a marker of the 13- cis retinal configuration in KR2 30 and inward proton pump Ns XeR 31 . Thus, our data suggest that the O 1 state of Er NaR contains 13- cis retinal, while O 2 has an all- trans retinal.…”

Section: Resultsmentioning

confidence: 98%

“…Due to spectral similarity, the region of the O 1 and O 2 intermediates is indicated as O 1/2 . The SBS abbreviation represents the “second bright state” signal at 335 nm being a marker of the 13- cis retinal configuration 30 , 31 . d Sodium dependence of the transient at 620 nm, indicative of the O 1 and O 2 intermediates, at pH 8.0.…”

Section: Resultsmentioning

confidence: 99%

A subgroup of light-driven sodium pumps with an additional Schiff base counterion

Podoliak,

Lamm,

Marin

et al. 2024

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Light-driven sodium pumps (NaRs) are unique ion-transporting microbial rhodopsins. The major group of NaRs is characterized by an NDQ motif and has two aspartic acid residues in the central region essential for sodium transport. Here we identify a subgroup of the NDQ rhodopsins bearing an additional glutamic acid residue in the close vicinity to the retinal Schiff base. We thoroughly characterize a member of this subgroup, namely the protein ErNaR from Erythrobacter sp. HL-111 and show that the additional glutamic acid results in almost complete loss of pH sensitivity for sodium-pumping activity, which is in contrast to previously studied NaRs. ErNaR is capable of transporting sodium efficiently even at acidic pH levels. X-ray crystallography and single particle cryo-electron microscopy reveal that the additional glutamic acid residue mediates the connection between the other two Schiff base counterions and strongly interacts with the aspartic acid of the characteristic NDQ motif. Hence, it reduces its pKa. Our findings shed light on a subgroup of NaRs and might serve as a basis for their rational optimization for optogenetics.

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A Detailed View on the (Re)isomerization Dynamics in Microbial Rhodopsins Using Complementary Near‐UV and IR Readouts

Asido,

Lamm,

Lienert

et al. 2024

Angewandte Chemie

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Isomerization is a key process in many (bio)chemical systems. In microbial rhodopsins, the photoinduced isomerization of the all‐trans retinal to the 13‐cis isomer initiates a cascade of structural changes of the protein. The interplay between these changes and the thermal relaxation of the isomerized retinal is one of the crucial determinants for rhodopsin functionality. It is therefore important to probe this dynamic interplay with chromophore specific markers that combine gapless temporal observation with spectral sensitivity. Here we utilize the near‐UV and mid‐IR fingerprint region in the framework of a systematic (time‐resolved) spectroscopic study on H+‐ (HsBR, (G)PR), Na+‐ (KR2, ErNaR) and Cl‐‐ (NmClR) pumps. We demonstrate that the near‐UV region is an excellent probe for retinal configuration and ‐ being sensitive to the electrostatic environment of retinal ‐ even transient ion binding, which allows us to pinpoint protein specific mechanistic nuances and chromophore‐charge interactions. The combination of the near‐UV and mid‐IR fingerprint region hence provides a spectroscopic analysis tool that allows a detailed, precise and temporally fully resolved description of retinal configurations during all stages of the photocycle.

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A Detailed View on the (Re)isomerization Dynamics in Microbial Rhodopsins Using Complementary Near‐UV and IR Readouts

Asido,

Lamm,

Lienert

et al. 2024

Angew Chem Int Ed

0

View full text Add to dashboard Cite

Isomerization is a key process in many (bio)chemical systems. In microbial rhodopsins, the photoinduced isomerization of the all‐trans retinal to the 13‐cis isomer initiates a cascade of structural changes of the protein. The interplay between these changes and the thermal relaxation of the isomerized retinal is one of the crucial determinants for rhodopsin functionality. It is therefore important to probe this dynamic interplay with chromophore specific markers that combine gapless temporal observation with spectral sensitivity. Here we utilize the near‐UV and mid‐IR fingerprint region in the framework of a systematic (time‐resolved) spectroscopic study on H+‐ (HsBR, (G)PR), Na+‐ (KR2, ErNaR) and Cl‐‐ (NmClR) pumps. We demonstrate that the near‐UV region is an excellent probe for retinal configuration and ‐ being sensitive to the electrostatic environment of retinal ‐ even transient ion binding, which allows us to pinpoint protein specific mechanistic nuances and chromophore‐charge interactions. The combination of the near‐UV and mid‐IR fingerprint region hence provides a spectroscopic analysis tool that allows a detailed, precise and temporally fully resolved description of retinal configurations during all stages of the photocycle.

show abstract

Vibrational Study of the Inward Proton Pump Xenorhodopsin NsXeR: Switch Order Determines Vectoriality

Cited by 4 publications

References 51 publications

A subgroup of light-driven sodium pumps with an additional Schiff base counterion

A subgroup of light-driven sodium pumps with an additional Schiff base counterion

A Detailed View on the (Re)isomerization Dynamics in Microbial Rhodopsins Using Complementary Near‐UV and IR Readouts

A Detailed View on the (Re)isomerization Dynamics in Microbial Rhodopsins Using Complementary Near‐UV and IR Readouts

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