Sandbox Reserved 931
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===Stabilization of the Trimeric Structure=== | ===Stabilization of the Trimeric Structure=== | ||
| - | L1ORF1p forms <scene name='57/579701/Orf1p_overall_structure/3'>homotrimers</scene> with unusually long alpha helices (residues 111-153), which create a coiled-coil structure | + | L1ORF1p forms <scene name='57/579701/Orf1p_overall_structure/3'>homotrimers</scene> with unusually long alpha helices (residues 111-153), which create a coiled-coil structure. The very long N-terminal helices are stabilized by three structural features: |
| - | * | + | *Coordination of <scene name='57/579701/Orf1p_overall_structure/6'>two chloride anions</scene> on the hydrophobic interface inside the coiled-coil structure by three asparagines (Asn142) and three arginines (Arg135). These promote the trimeric state of the coiled-coil domain; |
| - | * | + | *Externally stabilizing <scene name='57/579701/Orf1p_overall_structure/7'>hydrogen bonds</scene> between coiled-coil helices along the hydrophilic face of the helices; |
| - | * | + | *Water exclusion interactions within the internal hydrophobic face of the helices in the coiled-coil domain. |
| - | The trimerization is additionally stabilized on the C-terminal side of the molecule by 1 hydrogen bond between <scene name='57/579701/Orf1p_overall_structure/11'>each RRM</scene> domain, while the CTD regions remain more flexible and do not interact with one another | + | The trimerization is additionally stabilized on the C-terminal side of the molecule by 1 hydrogen bond between <scene name='57/579701/Orf1p_overall_structure/11'>each RRM</scene> domain, while the CTD regions remain more flexible and do not interact with one another. This might play a significant role in the accommodation of RNA molecules or during retrotransciption. |
===Nucleic Acid Binding Surfaces=== | ===Nucleic Acid Binding Surfaces=== | ||
Revision as of 07:07, 16 May 2014
| This Sandbox is Reserved from 01/04/2014, through 30/06/2014 for use in the course "510042. Protein structure, function and folding" taught by Prof Adrian Goldman, Tommi Kajander, Taru Meri, Konstantin Kogan and Juho Kellosalo at the University of Helsinki. This reservation includes Sandbox Reserved 923 through Sandbox Reserved 947. |
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LINE-1 ORF1 Protein
Long interspersed nuclear element 1 (LINE1) is a non-long terminal repeat (non-LTR) type retrotransposon in mammals that engages in retrotransposition - a process which randomly inserts LINE1's own coding sequence into the host genome, increasing the genome size and causing genomic instability. The LINE1 gene encodes the open reading frame 1 protein (L1ORF1p), which localizes to large L1 ribonucleoprotein particles, stress granules and nucleus (ref), and is required and necessary for retrotransposition.
Introduction
After transcription of the LINE1 gene, the same RNA transcript is both translated and is the template for reverse transcription. This RNA transcript contains two open reading frames: ORF1 and ORF2, which codes for two proteins, ORF1p and ORF2p. L1ORF1p contains the RNA packing and delivery functions, and L1ORF2p contains the enzymatic machinery for reverse transcription. Translation of both of these open reading frames is necessary for retrotransposition. The reverse transcribed LINE1 is integrated into the host genome in a different place than the original gene.
L1ORF1p localizes to ribonucleoprotein particles, stress granules and nucleus. Although the protein has general affinity to nucleic acids, it displays a strong cis preference, which makes it bind primarily encoding RNA transcripts ref. The role of L1ORF1p in retrotransposition is to protect the transcript from degradation and to help transport it to the nucleus.
Structure
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