Odorant binding protein: Difference between revisions
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Of all, the first role of OBP as an odorant solubilizer and carrier is generally accepted. | Of all, the first role of OBP as an odorant solubilizer and carrier is generally accepted. | ||
In order to explain the structure and function of these fascinating proteins, this page will further focus on a particular OBP - the well investigated ''[http://en.wikipedia.org/wiki/Bombyx_mori Bombyx mori]'' | In order to explain the structure and function of these fascinating proteins, this page will further focus on a particular OBP - the well investigated ''[http://en.wikipedia.org/wiki/Bombyx_mori Bombyx mori]'' pheromone binding protein: [http://www.uniprot.org/uniprot/P34174 BmorPBP]. | ||
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<StructureSection load='1ls8' size='340' side='right' caption='''Bombyx mori'' PBP -BmorPBP scene=''> | <StructureSection load='1ls8' size='340' side='right' caption='''Bombyx mori'' PBP -BmorPBP scene=''> | ||
Pheromone binding proteins (PBPs) are specialized members of the insect odorant-binding protein (OBP) super-family. | Pheromone binding proteins (PBPs) are specialized members of the insect odorant-binding protein (OBP) super-family. | ||
The main purpose in the | The main purpose in the adult moth's short life is reproduction. In fact, the male and female moth invest all of their energy and resources hoping to reach to the ultimate goal- mating. This long journey begins when the female moth releases a sex pheromone, usually in specific hours in the night <ref>doi: 10.1007/BF01946910</ref>. | ||
BmorPBP 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>, as the PBP of the first sex pheromone discovered ((E,Z)-10,12-hexadecadienol, or [http://en.wikipedia.org/wiki/Bombykol Bombykol]). The male moth needs to detect minute amount of the pheromone in the air, while following turbulent wind-born pheromone trail and response fast (experimental evidence shows a response time of 0.5 seconds<ref>doi: 10.1038/293161a0</ref>). | BmorPBP 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>, as the PBP of the first sex pheromone discovered ((E,Z)-10,12-hexadecadienol, or [http://en.wikipedia.org/wiki/Bombykol Bombykol]). The male moth needs to detect minute amount of the pheromone in the air, while following turbulent wind-born pheromone trail and response fast (experimental evidence shows a response time of 0.5 seconds<ref>doi: 10.1038/293161a0</ref>). | ||
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[[Image:A to b with ligand.png|thumb|upright=2|The A and B forms with ligand (PDB IDs: [[1gm0]] and [[1ls8]]).]] | [[Image:A to b with ligand.png|thumb|upright=2|The A and B forms with ligand (PDB IDs: [[1gm0]] and [[1ls8]]).]] | ||
BmorPBP has two conformations: The '''"closed form" (A)''' and the ''"open form" (B)''<ref>DOI: 10.1074/jbc.274.43.30950</ref>. The bombykol and the alpha-helix | BmorPBP has two conformations: The '''"closed form" (A)''' and the ''"open form" (B)''<ref>DOI: 10.1074/jbc.274.43.30950</ref>. The bombykol and the alpha-helix located in the c-terminus of the protein compete for the binding site: when the c-terminus is inside the binding cavity it get's an alpha helix shape, and the protein is in its "close form" (B), whereas in the "open form" (A) the c-terminus is outside of the protein and has no defined secondary structure. Binding experiments have shown that the B-form binds 15 times higher than the A-form <ref>doi: 10.1073/pnas.0501447102</ref>, therefore considered to be the carrier of the pheromone. The complex of the A-form and the pheromone, is then considered the form that activates the receptor. | ||
The <scene name='68/683383/1dqe-1gm0/4'>transition between the two conformation</scene> is both pH and ligand dependent <ref>doi: 10.1073?pnas.251532998</ref><ref>DOI: 10.1016/j.bbrc.2005.07.176</ref><ref>doi: 10.1073/pnas.1317706110</ref>. In short, the B-form (c-terminus outside the cavity) occurs only at neutral pH and in the presence of the ligand. The A-form (c-terminus inside the cavity) occurs at both low and neutral pH, yet at the latter only in the absence of ligand. Therefore, in neutral pH when the ligand is binding to the protein in its A-form, the complex formation causes a change in conformation to the B-form. However, both A and B forms are equally distributed in the lymph. | The <scene name='68/683383/1dqe-1gm0/4'>transition between the two conformation</scene> is both pH and ligand dependent <ref>doi: 10.1073?pnas.251532998</ref><ref>DOI: 10.1016/j.bbrc.2005.07.176</ref><ref>doi: 10.1073/pnas.1317706110</ref>. In short, the B-form (c-terminus outside the cavity) occurs only at neutral pH and in the presence of the ligand. The A-form (c-terminus inside the cavity) occurs at both low and neutral pH, yet at the latter only in the absence of ligand. Therefore, in neutral pH when the ligand is binding to the protein in its A-form, the complex formation causes a change in conformation to the B-form. However, both A and B forms are equally distributed in the lymph. | ||
