Bestrhodopsins constitute a class of light-regulated pentameric ion channels that consist of one or two rhodopsins in tandem fused with bestrophin ion channel domains. Here, we report on the isomerization dynamics in the rhodopsin tandem domains of Phaeocystis antarctica bestrhodopsin, which binds all-trans retinal Schiff-base (RSB) absorbing at 661 nm and, upon illumination, converts to the meta-stable P540 state with an unusual 11-cis RSB. The primary photoproduct P682 corresponds to a mixture of highly distorted 11-cis and 13-cis RSB directly formed from the excited state in 1.4 ps. P673 evolves from P682 in 500 ps and contains highly distorted 13-cis RSB, indicating that the 11-cis fraction in P682 converts to 13-cis. Next, P673 establishes an equilibrium with P595 in 1.2 µs, during which RSB converts to 11-cis and then further proceeds to P560 in 48 µs and P540 in 1.0 ms while remaining 11-cis. Hence, extensive isomeric switching occurs on the early ground state potential energy surface (PES) on the hundreds of ps to µs timescale before finally settling on a metastable 11-cis photoproduct. We propose that P682 and P673 are trapped high up on the ground-state PES after passing through either of two closely located conical intersections that result in 11-cis and 13-cis RSB. Co-rotation of C11=C12 and C13=C14 bonds results in a constricted conformational landscape that allows thermal switching between 11-cis and 13-cis species of highly strained RSB chromophores. Protein relaxation may release RSB strain, allowing it to evolve to a stable 11-cis isomeric configuration in microseconds.

• Klíčová slova
• conical intersection, far-red absorbing rhodopsin, femtosecond stimulated Raman spectroscopy, femtosecond to millisecond spectroscopy, multiple retinal isomerization,
• MeSH
• diterpeny * MeSH
• isomerie MeSH
• konformace proteinů MeSH
• retinaldehyd * chemie   MeSH
• rodopsin * metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• 13-cis-retinal MeSH Prohlížeč
• diterpeny * MeSH
• retinaldehyd * MeSH
• rodopsin * MeSH

Schizorhodopsins (SzRs), a rhodopsin family first identified in Asgard archaea, the archaeal group closest to eukaryotes, are present at a phylogenetically intermediate position between typical microbial rhodopsins and heliorhodopsins. However, the biological function and molecular properties of SzRs have not been reported. Here, SzRs from Asgardarchaeota and from a yet unknown microorganism are expressed in Escherichia coli and mammalian cells, and ion transport assays and patch clamp analyses are used to demonstrate SzR as a novel type of light-driven inward H+ pump. The mutation of a cytoplasmic glutamate inhibited inward H+ transport, suggesting that it functions as a cytoplasmic H+ acceptor. The function, trimeric structure, and H+ transport mechanism of SzR are similar to that of xenorhodopsin (XeR), a light-driven inward H+ pumping microbial rhodopsins, implying that they evolved convergently. The inward H+ pump function of SzR provides new insight into the photobiological life cycle of the Asgardarchaeota.

• MeSH
• Archaea genetika   metabolismus   MeSH
• buněčná membrána metabolismus   MeSH
• fluorescenční protilátková technika MeSH
• gating iontového kanálu účinky záření   MeSH
• konformace proteinů MeSH
• molekulární modely MeSH
• multigenová rodina MeSH
• mutace MeSH
• protonové pumpy chemie   genetika   metabolismus   MeSH
• rodopsin chemie   genetika   metabolismus   MeSH
• spektroskopie infračervená s Fourierovou transformací MeSH
• světlo MeSH
• vztahy mezi strukturou a aktivitou MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• protonové pumpy MeSH
• rodopsin MeSH