TCDB is operated by the Saier Lab Bioinformatics Group
« See all members of the family


3.E.1.7.2
Channelrhodopsin-2 (chlamyrhodopsin-4; ChR2; CR2; Cop4; CSOB) (light-gated cation-selective ion channel (both monovalent and divalent cations are transported)) (Nagel et al., 2003). Berndt et al. (2010) showed that ChR2 has two open states with differing ion selectivities. The channel is fairly nonspecific at the beginning of a light pulse, and becomes more specific for protons during longer periods of light exposure. Residues involved in channel closure have been identified (Bamann et al. 2010).  ChR2 is 712 aas long; the MR domain is N-terminal (Lee et al. 2015). The free energy profiles computed for proton transfer to the counterion, either via a direct jump or mediated by a water molecule, demonstrate that, when retinal is all-trans, water and protein electrostatic interactions largely favour the protonated retinal Schiff base state (Adam and Bondar 2018).
   Blue light illumination of ChR2 activates an intrinsic leak channel conductive for cations. Sequence comparison of ChR2 with the related ChR1 protein revealed a cluster of charged amino acids within the predicted transmembrane domain 2 (TM2), which includes glutamates E90, E97 and E101. Charge inversion substitutions altered ChR2 function, replacement of E90 by lysine or alanine resulted in differential effects on H+- and Na+-mediated currents. These results are consistent with this glutamate side chain within TMS2 contributing to ion flux through and the cation selectivity of ChR2 (Ruffert et al., 2011). Glutamate residue-97 lies in the outer pore where it interacts with a cation to facilitate dehydration. This residue is also the primary binding target of Gd3+(Tanimoto et al., 2012).  Channelrhodopsin has been converted into a light-gated chloride channel (Wietek et al. 2014).  TMSs 2, 6 and 7 reorient or rearrange during the photocycle with no major differences near TMSs 3 and 4 at the dimer interface. TMS2 plays a key role in light-induced channel opening and closing in ChR2 (Müller et al. 2015).  Negative charges at the extracellular side of transmembrane domain 7 funnel cations into the pore (Richards and Dempski 2015).  CrChR2, is the most widely used optogenetic tool in neuroscience.  Water efflux and the cessation of the ion conductance are synchronized (Lórenz-Fonfría et al. 2015).  light and pH induce changes in the structure and accessibility of TMSB (Volz et al. 2016). Residues V86, K93 and N258 form a putative barrier to ion translocation. These residues contribute to cation selectivity (V86 and N258), the transition between the two open states (V86), open channel stability, and the hydrogen-bonding network (K93I and K93N) (Richards and Dempski 2017). The x-ray structure is available and reveals much about the mechanism of channel regulation (Gerwert 2017; Volkov et al. 2017).

Accession Number:Q8RUT8
Protein Name:Channelrhodopsin-2
Length:737
Molecular Weight:77247.00
Species:Chlamydomonas reinhardtii [3055]
Number of TMSs:4
Location1 / Topology2 / Orientation3: Basolateral cell membrane1 / Multi-pass membrane protein2
Substrate monovalent cations, divalent cations

Cross database links:

RefSeq: XP_001701725.1   
Entrez Gene ID: 5727376   
Pfam: PF01036   
KEGG: cre:CHLREDRAFT_   

Gene Ontology

GO:0016020 C:membrane
GO:0005216 F:ion channel activity
GO:0006811 P:ion transport

References (2)

[1] “The Chlamydomonas genome reveals the evolution of key animal and plant functions.”  Merchant S.S.et.al.   17932292
[2] “Two rhodopsins mediate phototaxis to low- and high-intensity light in Chlamydomonas reinhardtii.”  Sineshchekov O.A.et.al.   12060707
Structure:
3UG9   4YZI     

External Searches:

  • Search: DB with
  • BLAST ExPASy (Swiss Institute of Bioinformatics (SIB) BLAST)
  • CDD Search (Conserved Domain Database)
  • Search COGs (Clusters of Orthologous Groups of proteins)
  • 2° Structure (Network Protein Sequence Analysis)

Analyze:

Predict TMSs (Predict number of transmembrane segments)
Window Size: Angle:  
Window Size: Angle:  
FASTA formatted sequence
1:	MDYGGALSAV GRELLFVTNP VVVNGSVLVP EDQCYCAGWI ESRGTNGAQT ASNVLQWLAA 
61:	GFSILLLMFY AYQTWKSTCG WEEIYVCAIE MVKVILEFFF EFKNPSMLYL ATGHRVQWLR 
121:	YAEWLLTCPV ILIHLSNLTG LSNDYSRRTM GLLVSDIGTI VWGATSAMAT GYVKVIFFCL 
181:	GLCYGANTFF HAAKAYIEGY HTVPKGRCRQ VVTGMAWLFF VSWGMFPILF ILGPEGFGVL 
241:	SVYGSTVGHT IIDLMSKNCW GLLGHYLRVL IHEHILIHGD IRKTTKLNIG GTEIEVETLV 
301:	EDEAEAGAVN KGTGKYASRE SFLVMRDKMK EKGIDVRASL DNSKEVEQEQ AARAAMMMMN 
361:	GNGMGMGMGM NGMNGMGGMN GMAGGAKPGL ELTPQLQPGR VILAVPDISM VDFFREQFAQ 
421:	LSVTYELVPA LGADNTLALV TQAQNLGGVD FVLIHPEFLR DRSSTSILSR LRGAGQRVAA 
481:	FGWAQLGPMR DLIESANLDG WLEGPSFGQG ILPAHIVALV AKMQQMRKMQ QMQQIGMMTG 
541:	GMNGMGGGMG GGMNGMGGGN GMNNMGNGMG GGMGNGMGGN GMNGMGGGNG MNNMGGNGMA 
601:	GNGMGGGMGG NGMGGSMNGM SSGVVANVTP SAAGGMGGMM NGGMAAPQSP GMNGGRLGTN 
661:	PLFNAAPSPL SSQLGAEAGM GSMGGMGGMS GMGGMGGMGG MGGAGAATTQ AAGGNAEAEM 
721:	LQNLMNEINR LKRELGE