Although many microbial rhodopsins have been discovered many of organisms in a variety of habitats, little is known about the property and diversity of rhodopsin in flavobacteria. Recent studies discovered that many proteorhodopsin (PR)-like proteins exist in genomes of flavobacteria. Following the isolation of a flavobacterial rhodopsins (FR) from the flavobacteria IMCC1997 from the East Sea of Korea, we characterized its photochemical features. We confirmed that the FR expression is induced by light in the IMCC1997 cell. Upon receiving light energy in vitro, the proton acceptor (D83) and donor (E94) of the FR translocate protons from intracellular to extracellular regions. Compared with proteorhodopsin (PR), the FR from IMCC 1997 cells is very unstable, which may be explained by their primary sequence differences. The ratio of all trans/13-cis retinal conformation does not influence this stability. To measure the stability of FR, we tested heat endurance at 70 °C and found that the heat endurance time of some FR mutants increased. Based upon these results, we found the helix E of this protein to be critical for the unstability of FR.

中文翻译：

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黄细菌视紫红质的光化学特征：螺旋E区对于热稳定性的重要性。

尽管已经发现了许多微生物视紫红质，它们存在于各种生境中，但对于黄细菌中视紫红质的性质和多样性知之甚少。最近的研究发现，黄细菌基因组中存在许多类视紫红质（PR）样蛋白。从韩国东海的黄杆菌IMCC1997中分离出黄细菌视紫红质（FR）之后，我们表征了其光化学特征。我们证实，在IMCC1997细胞中，FR表达是由光诱导的。体外接受光能后，FR的质子受体（D83）和供体（E94）将质子从细胞内转移到细胞外区域。与蛋白视紫红质（PR）相比，来自IMCC 1997细胞的FR非常不稳定，这可以用它们的主要序列差异来解释。所有反式/ 13-顺式视网膜构象的比例不影响这种稳定性。为了测量FR的稳定性，我们在70°C下测试了耐热性，发现某些FR突变体的耐热时间增加了。基于这些结果，我们发现该蛋白的螺旋E对FR的不稳定至关重要。