Bacteriorhodopsin is a photosynthetic pigment used by archaea, most notably halobacteria. It acts as a proton pump, i.e. it captures light energy and uses it to move protons across the membrane out of the cell. The resulting proton gradient is subsequently converted into chemical energy. A photosynthetic pigment is a pigment present in chloroplasts or photosynthetic bacteria which provides the energy necessary for photosynthesis. ... Phyla / Classes Phylum Crenarchaeota Phylum Euryarchaeota     Halobacteria     Methanobacteria     Methanococci     Methanopyri     Archaeoglobi     Thermoplasmata     Thermococci Phylum Korarchaeota Phylum Nanoarchaeota Archaea (; from Greek αρχαία, old ones; singular Archaeum, Archaean, or Archaeon), also called Archaebacteria (), is a major division of living organisms. ... Genera Haloarcula Halobacterium Halobaculum Halococcus Haloferax Halogeometricum Halorubrum Haloterrigena Natrialba Natrinema Natronobacterium Natronococcus Natronomonas Natronorubrum The halobacteria are a family of archaea, found in water saturated or nearly saturated with salt. ... A proton pump is an integral membrane protein that is capable of moving protons across the membrane of a cell, mitochondrion, or other subcellular compartment, thereby creating a difference or gradient in both pH and electrical charge (ignoring differences in buffer capacity) and tending to establish an electrochemical potential. ... Properties [1][2] In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ...

Bacteriorhodopsin is an integral membrane protein usually found in two-dimensional crystalline patches known as "purple membrane", which can occupy up to nearly 50% of the surface area of the archaeal cell. The repeating element of the hexagonal lattice is composed of three identical protein chains, each rotated by 120 degrees relative to the others. Each chain has seven transmembrane alpha helices and contains one molecule of retinal buried deep within. It is the retinal molecule that changes its conformation when absorbing a photon, resulting in a conformational change of the surrounding protein and the proton pumping action. An Integral Membrane Protein (IMP) is a protein molecule (or assembly of proteins) that is permanently attached to the biological membrane. ... Within an integral membrane protein, a transmembrane helix is a segment that is alpha-helical in structure, roughly 20 amino acids in length and (though it may be presumed to lie within the protein, out of contact with the surrounding lipid bilayer) is said to span the membrane. ... In the vision system, retinal, technically called retinene1 or retinaldehyde, is a light-sensitive retinene molecule found in the photoreceptor cells of the retina. ... The word light is defined here as electromagnetic radiation of any wavelength; thus, X-rays, gamma rays, ultraviolet light, microwaves, radio waves, and visible light are all forms of light. ...

The bacteriorhodopsin molecule is purple and is most efficient at absorbing green light (wavelength 500-650 nm, with the absorption maximum at 568 nm). A nanometre (American spelling: nanometer) is 1. ...

The three-dimensional tertiary structure of bacteriorhodopsin resembles that of vertebrate rhodopsins, the pigments that sense light in the retina. Rhodopsins also contain retinal, however the functions of rhodopsin and bacteriorhodopsin are different and there is no homology of their amino acid sequences. Both rhodopsin and bacteriorhodopsin belong to the 7TM receptor family of proteins, but rhodopsin is a G protein coupled receptor and bacteriorhodopsin is not. In the first use of electron crystallography to obtain an atomic-level protein structure, the structure of bacteriorhodopsin was resolved in 1990. It was then used as a template to build models of other G protein-coupled receptors before crystallographic structures were also available for these proteins. In biochemistry, the tertiary structure of a protein is its overall shape. ... Classes and Clades See below Vertebrates are members of the subphylum Vertebrata (within the phylum Chordata), specifically, those chordates with backbones or spinal columns. ... A rhodopsin molecule (yellow) with bound retinal (orange), embedded in a cell membrane (lipids shown as green, head groups as red/blue). ... For animal and plant pigments, see Pigment, biology. ... Human eye cross-sectional view. ... In biology, two or more structures are said to be homologous if they are alike because of shared ancestry. ... The general structure of an α-amino acid molecule, with the amine group on the left and the carboxyl group on the right. ... In cell biology, G-protein-coupled receptors, also known as GPCR, seven transmembrane receptors, heptahelical receptors, or 7TM receptors, are a class of transmembrane receptors. ... In cell biology, G-protein-coupled receptors, also known as GPCR, seven transmembrane receptors, heptahelical receptors, or 7TM receptors, are a class of transmembrane receptors. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Proteins are amino acid chains, made up from 20 different L-α-amino acids, also referred to as residues, that fold into unique three-dimensional protein structures. ... This article is about the year. ... Enargite crystals In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ...

Many molecules have homology to bacteriorhodopsin, including the light-driven chloride pump halorhodopsin, and some directly light-activated channels like channelrhodopsin. Halorhodopsin is a light-driven ion pump, specific for chloride ions, and found in phylogenetically ancient bacteria (archaea), known as halobacteria. ... Channelrhodopsins are ion channels that are directly opened by light. ...

All other photosynthetic systems in bacteria, algae and plants use chlorophylls or bacteriochlorophylls rather than bacteriorhodopsin. These also produce a proton gradient, but in a quite different and more indirect way involving an electron transfer chain consisting of several other proteins. Furthermore, chlorophylls are aided in capturing light energy by other pigments known as "antennas"; these are not present in bacteriorhodopsin based systems. Lastly, chlorophyll-based photosynthesis is coupled to carbon fixation (the incorporation of carbon dioxide into larger organic molecules); this is not true for bacteriorhodopsin-based system. It is thus likely that photosynthesis independently evolved at least twice, once in bacteria and once in archaea. Chlorophyll is a green photosynthetic pigment found in plants, algae, and cyanobacteria. ... Bacteriochlorophylls are photosynthetic pigments that occur in various bacteria. ... The electron transfer chain (also called the electron transport chain, ETC, e-train, or simply electron transport), is any series of protein complexes and lipid-soluble messengers that convert the reductive potential of energized electrons into a cross-membrane proton gradient. ... Carbon fixation is a process found in autotrophs, usually driven by photosynthesis, whereby carbon dioxide is converted into organic compounds. ... Carbon dioxide is a chemical compound composed of one carbon and two oxygen atoms. ...

External links

• Bacteriorhodopsin - PDB molecule of the month
• Calculated spatial positions of bacteriorhodopsin-like proteins in membrane