Sandbox Reserved 1265
From Proteopedia
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Human Pre-initiation complex is an octameric molecule - it is composed of 8 polypeptide chain subunits. | Human Pre-initiation complex is an octameric molecule - it is composed of 8 polypeptide chain subunits. | ||
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| + | <scene name='75/751158/Prevalence_of_alpha_helices/1'>All subunits are largely composed of alpha helices.</scene> | ||
The 43S initiation complex forms when Methionine initiation tRNA (Met-tRNAi(Met)) forms a ternary complex with Eukaryotic Initiation factor 2 (EIF2) and GTP. This complex then binds to the 40S subunit of the ribosome alongside EIF3, EIF1, and EIF1A. Finally, DHX29, a protein that aids structured mRNA scanning, binds to the 40S subunit as well. | The 43S initiation complex forms when Methionine initiation tRNA (Met-tRNAi(Met)) forms a ternary complex with Eukaryotic Initiation factor 2 (EIF2) and GTP. This complex then binds to the 40S subunit of the ribosome alongside EIF3, EIF1, and EIF1A. Finally, DHX29, a protein that aids structured mRNA scanning, binds to the 40S subunit as well. | ||
<StructureSection load='3j8c' size='340' side='right' caption='View of the full octamer complex''> | <StructureSection load='3j8c' size='340' side='right' caption='View of the full octamer complex''> | ||
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| + | <scene name='75/751158/Subunit_polypeptides/1'>This view indicates the directional conformation of each subunit's primary structure, with each polypeptide's 5' N-terminus marked in blue, and the 3' H-terminus marked in red.</scene> | ||
==Function== | ==Function== | ||
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==Interactions== | ==Interactions== | ||
| - | The complex assembles around the 5' end of mRNA, and then proceeds to scan along the molecule in the 3' direction. | + | The complex assembles around the 5' end of mRNA, and then proceeds to scan along the molecule in the 3' direction. Upon identifying the Kozak sequence, which has the start codon (AUG) embedded within it, the pre-initiation complex binds and begins to recruit the other protein factors necessary for translation. |
The assembly and operation of Human PIC occurs entirely in the cytosol. | The assembly and operation of Human PIC occurs entirely in the cytosol. | ||
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| + | <scene name='75/751158/Alpha_helices/1'>As seen in the red ball-and-stick subunit, the alpha helices take on a very ordered, parallel orientation in most of the subunits, similar in many respects to transmembrane proteins, which may affect how they interact.</scene> | ||
== Origin == | == Origin == | ||
3j8c originates in ''Homo sapiens'', but similar proteins are found in virtually all eukaryotes. | 3j8c originates in ''Homo sapiens'', but similar proteins are found in virtually all eukaryotes. | ||
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| + | Prokaryotes do not have a corresponding initiation complex - instead, most have some deviation of the Shine-Dalgarno sequence in the 5' untranslated region that the 30s ribosomal subunit binds to in order to initiate translation. | ||
== References == | == References == | ||
<references/> | <references/> | ||
| + | http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=3J8C | ||
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| + | http://www.proteopedia.org/wiki/index.php/3j8c | ||
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| + | http://www.rcsb.org/pdb/explore.do?structureId=3j8c | ||
Current revision
Human Pre-initiation Complex (3j8c)
Structure
Human Pre-initiation complex is an octameric molecule - it is composed of 8 polypeptide chain subunits.
The 43S initiation complex forms when Methionine initiation tRNA (Met-tRNAi(Met)) forms a ternary complex with Eukaryotic Initiation factor 2 (EIF2) and GTP. This complex then binds to the 40S subunit of the ribosome alongside EIF3, EIF1, and EIF1A. Finally, DHX29, a protein that aids structured mRNA scanning, binds to the 40S subunit as well.
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