title: Glutamate residue 90 in the predicted transmembrane domain 2 is crucial for cation flux through channelrhodopsin 2.
abstract: Channelrhodopsin 2 (ChR2) is a microbial-type rhodopsin with a putative heptahelical structure that binds all-trans-retinal. 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 of these residues significantly altered ChR2 function as revealed by two-electrode voltage-clamp recordings of light-induced currents from Xenopus laevis oocytes expressing the respective mutant proteins. Specifically, replacement of E90 by lysine or alanine resulted in differential effects on H(+)- and Na(+)-mediated currents. Our results are consistent with this glutamate side chain within the proposed TM2 contributing to ion flux through and the cation selectivity of ChR2.
authors.affiliation: Department of Neurochemistry, Max-Planck Institute for Brain Research, 60528 Frankfurt, Germany.
authors.forename: Karelia
authors.initials: K
authors.lastname: Ruffert
authors.forename: Bettina
authors.initials: B
authors.lastname: Himmel
authors.forename: Deepti
authors.initials: D
authors.lastname: Lall
authors.forename: Christian
authors.initials: C
authors.lastname: Bamann
authors.forename: Ernst
authors.initials: E
authors.lastname: Bamberg
authors.forename: Heinrich
authors.initials: H
authors.lastname: Betz
authors.forename: Volker
authors.initials: V
authors.lastname: Eulenburg
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002412:Cations / Q000378:metabolism; D016825:Chlamydomonas reinhardtii / Q000235:genetics / Q000378:metabolism; D018698:Glutamic Acid / Q000737:chemistry / Q000235:genetics; D006863:Hydrogen-Ion Concentration; D017136:Ion Transport; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary / Q000235:genetics; D012243:Rhodopsin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis
chemical_list: D002412:Cations; D018698:Glutamic Acid; D012243:Rhodopsin