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Odorant binding protein
From Proteopedia
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====BmorPBP structure and function==== | ====BmorPBP structure and function==== | ||
This protein was first identified in the ''B. mori'' male antennae by Krieger et al. in 1996 <ref>doi: 10.1016/0965-1748(95)00096-8</ref> . | This protein was first identified in the ''B. mori'' male antennae by Krieger et al. in 1996 <ref>doi: 10.1016/0965-1748(95)00096-8</ref> . | ||
| - | It has 164 amino acids that forms 6-7 alpha helices. Three 3 disulfide bonds formed by 6 cystein residues tied four helices. As expected from a soluble protein, its surface is covered with [[charged residues]]. | + | It has 164 amino acids that forms 6-7 alpha helices. Three 3 disulfide bonds formed by [[6 cystein]] residues tied four helices. As expected from a soluble protein, its surface is covered with [[charged residues]]. |
======BmorPBP ligand and ligand binding====== | ======BmorPBP ligand and ligand binding====== | ||
| - | The protein natural ligand is the moth pheromone bombykol. However, it was demonstrated that other molecules can also bound to the protein cavity <ref>doi: 10.1016/j.str.2007.07.013</ref>. The interaction with the ligand is beeing made by 4 alpha helices in the core of the protein, which form the binding cavity <ref>doi: 10.1016/S1074-5521(00)00078-8</ref>. | + | The protein natural ligand is the moth pheromone bombykol. However, it was demonstrated that other molecules can also bound to the protein cavity <ref>doi: 10.1016/j.str.2007.07.013</ref>. The interaction with the ligand is beeing made by [[4 alpha helices]] in the core of the protein, which form the binding cavity <ref>doi: 10.1016/S1074-5521(00)00078-8</ref>. |
| - | The hydroxyl group of the pheromone bombykol forms a [[hydrogen bond with the sidechain of Ser56]] (O–O distance of 2.8 Å). | + | The [[hydroxyl group]] of the pheromone bombykol forms a [[hydrogen bond with the sidechain of Ser56]] (O–O distance of 2.8 Å). |
======Protein conformations====== | ======Protein conformations====== | ||
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In a nuetral pH (6.5-7) the protein is in the "open form" (A), in which the | In a nuetral pH (6.5-7) the protein is in the "open form" (A), in which the | ||
| - | The | + | The transition between the two conformation is taking place between 6-5 pH. |
| - | . Of these, residues Asp-132 and Glu-141 | + | The C terminus of the protein bears mostly [[nonpolar amino acids]]. Yet on the surface of the helix there are [[three exceptional amino acids]]: Asp-132, Glu-137, and Glu-141, which are conserved in moth PBP <ref>10.1016/j.bbrc.2005.07.176</ref>. Of these, residues Asp-132 and Glu-141 triggers the formation of the α-helix upon protonation at low pH. This what is causing the ejacullate of the ligand from the binding pocket, which is replaced by the formated alpha helix<ref>doi: 10.1016/j.bbrc</ref>. |
*[["open form" (A)]] | *[["open form" (A)]] | ||
*[["close form" (B)]] | *[["close form" (B)]] | ||
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| - | *'''The pH dependent theory''' | ||
| - | According to this theory, | ||
====Receptor activation==== | ====Receptor activation==== | ||
| + | Two theories have been propsed for the activation of the odorant receptors located on the dendrtirte membrane. One theory suggests that the pheromone-PBP complex is needed for the receptor activation, while the second theory argue that the pheromone itself is sufficient for the activation of the receptor. | ||
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| + | *'''Activation by the complex pheromone-PBP''' | ||
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| + | *'''Activation by the pheromone alone''' | ||
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The surface of the dendrite is negatively charged <ref>DOI: 10.1016/0040-8166(84)90004-1</ref>, which cause the accumulation of positively charged kations near the membrane surface (20-50 nm), thereby inducing a low pH environment near the dendrite membrane [[kaissling 2009]] | The surface of the dendrite is negatively charged <ref>DOI: 10.1016/0040-8166(84)90004-1</ref>, which cause the accumulation of positively charged kations near the membrane surface (20-50 nm), thereby inducing a low pH environment near the dendrite membrane [[kaissling 2009]] | ||
Leal WS, et al. (2005) Kinetics and molecular properties of pheromone binding and release. Proc Natl Acad Sci USA 102(15):5386–5391. | Leal WS, et al. (2005) Kinetics and molecular properties of pheromone binding and release. Proc Natl Acad Sci USA 102(15):5386–5391. | ||
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| - | *'''The other theory''' | ||
Revision as of 15:41, 9 January 2015
Contents |
Introduction
Odorant-binding protein (OBP) are soluble proteins which involve in the processes of odorant detection in the olfactory sensilla.
The first OBP that was identified is Bovine odorant binding protein, that was isolated from a cow's mucus ref. Though functunaly same, vertebrates and insects OBP are stucture and different.
OBPs are important for insect olfaction. For instance, OBP76a (LUSH) in the fly Drosophila melanogaster is required for the detection of the pheromone vaccenyl acetate [Ha and Smith, 2006; Xu et al., 2005] and has been proven to adopt a conformation that activates the odorant receptor [Laughlin et al., 2008].
OBP in insects
OBP Function
Despite three decades of intensive research, the exact roles of OBP and the mechanism by which the odorant receptor (OR) is activated are still in dispute [1][2]. Of all, the role of OBP as an odorant carrier is generally accepted.
A few functions have been suggested for OBP: 1. 2. 3. 4.
In order to explain the structure and function of these fascinating proteins, this page will further focus on a particular OBP - the well investigated Bombyx mori PBP: BmorPBP.
PBP
PBPs are specialized members of the insect odorant-binding protein (OBP) super-family, and they are devided into three groups by their lengths: long-chain PBPs (∼160 aa), medium-chain PBPs (∼120 aa), and short-chain PBPs (∼110 aa) [3]
Bombyx mori BmorPBP (lets talk about sex..)
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See also
References
Proteopedia Page Contributors and Editors (what is this?)
Nurit Eliash, Michal Harel, Joel L. Sussman, Alexander Berchansky, Jaime Prilusky
