Conversion of microbial rhodopsins: insights into functionally essential elements and rational protein engineering

Abstract

Technological progress has enabled the successful application of functional conversion to a variety of biological molecules, such as nucleotides and proteins. Such studies have revealed the functionally essential elements of these engineered molecules, which are difficult to characterize at the level of an individual molecule. The functional conversion of biological molecules has also provided a strategy for their rational and atomistic design. The engineered molecules can be used in studies to improve our understanding of their biological functions and to develop protein-based tools. In this review, we introduce the functional conversion of membrane-embedded photoreceptive retinylidene proteins (also called rhodopsins) and discuss these proteins mainly on the basis of results obtained from our own studies. This information provides insights into the molecular mechanism of light-induced protein functions and their use in optogenetics, a technology which involves the use of light to control biological activities.

Biological Optical-to-Chemical Signal Conversion Interface: A Small-Scale Modulator for Molecular Communications

“…Throughout this paper, we use "GR" and "bacteriorhodopsin" interchangeably. porting rhodopsins, there are also sensory rhodopsins functioning as light-signal transducers in nature [23]. Therefore, natural organisms make use of light not only as energy source but also as information signal, similar to the proposed modulator.…”

Light‐Controlled Mammalian Cells and Their Therapeutic Applications in Synthetic Biology

“…They can be categorized into two major classes: microbial opsins (type I) and invertebrate/vertebrate opsins (type II). [39] Nonneural optogenetics (i.e., non-ion flux-based optogenetics) usually employs nonopsin photoactivatable proteins or gene switches. [6] In addition to type I and II opsins, there are some engineered variants of opsins, which usually combine features of type I and type II opsins.…”

“…Gαq subunit-dependent signaling is linked to increased levels of inositol-3-phosphate (IP3) and diacylglycerol (DAG), whereas Gαt signaling mainly results in lowered cGMP levels that trigger subsequent signal amplification steps in photoreceptor cells of the mammalian retina. [39,42] Melanopsin, a representative member of animal opsins, is endogenously expressed in intrinsically photosensitive retinal ganglion cells (ipRGCs) of the inner retina. These membrane-bound GPC photoreceptors are retinal-dependent.…”

“…[39,42] However, microbial opsins show little or no G-protein activation [47,48] and unlike their mammalian counterparts, microbial opsins (type I) isomerize all-trans-retinal to 13-cis-retinal upon illumination ( Figure 1b); this reverts to all-trans-retinal within the receptor during an inactive recovery phase. [39,42] However, microbial opsins show little or no G-protein activation [47,48] and unlike their mammalian counterparts, microbial opsins (type I) isomerize all-trans-retinal to 13-cis-retinal upon illumination ( Figure 1b); this reverts to all-trans-retinal within the receptor during an inactive recovery phase.…”

Optogenetics and vision

“…В качестве деполяризующего инструмента в оптогенетике широко используется катионный канальный родопсин из одноклеточной зелёной водоросли хламидомонады Chlamydomonas reinhardii. Благодаря успехам современной биоинженерии семейство канальных родопсинов стремительно расширяется, их характеристики существенно улучшаются [5].…”