title: Low-resolution characterization of the 3D structure of the Euglena gracilis photoreceptor.
abstract: This paper deals with the first characterization of the structure of the photoreceptive organelle of the unicellular alga Euglena gracilis (Euglenophyta). This organelle has a three-dimensional organization consisting of up to 50 closely stacked membrane lamellae. Ionically induced unstacking of the photoreceptor lamellae revealed ordered arrays well suited to structural analysis by electron microscopy and image analysis, which ultimately yielded a low-resolution picture of the structure. Each lamella is formed by the photoreceptive membrane protein of the cell assembled within the membrane layer in a hexagonal lattice. The first order diffraction spots in the calculated Fourier transform reveals the presence of 6-fold symmetrized topography (better resolution about 90A). The 2D and 3D structural data are very similar with those recently published on proteorodopsin, a membrane protein used by marine bacterio-plankton as light-driven proton pump. In our opinion these similarity indicate that a photoreceptive protein belonging to the same superfamily of proteorodopsin could form the Euglena photoreceptor.
authors: Istituto di Biofisica, Via Moruzzi 1, 56124 Pisa, Italy.
authors: Laura
authors: L
authors: Barsanti
authors: Primo
authors: P
authors: Coltelli
authors: Valtere
authors: V
authors: Evangelista
authors: Vincenzo
authors: V
authors: Passarelli
authors: Anna Maria
authors: AM
authors: Frassanito
authors: Nicoletta
authors: N
authors: Vesentini
authors: Paolo
authors: P
authors: Gualtieri
mesh_terms: D020418:Algal Proteins / Q000648:ultrastructure*; D000818:Animals; D005056:Euglena gracilis / Q000378:metabolism* / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D017956:Photoreceptor Cells, Invertebrate / Q000648:ultrastructure*; D015800:Protozoan Proteins / Q000648:ultrastructure*
chemical_list: D020418:Algal Proteins; D015800:Protozoan Proteins