Sandbox Reserved 1273
From Proteopedia
| (38 intermediate revisions not shown.) | |||
| Line 1: | Line 1: | ||
| - | + | = tRNA fMet = | |
| - | == | + | |
| - | + | ||
| - | + | ||
| - | + | ||
| - | == | + | <Structure load='3cw6' size='350' frame='true' align='right' caption='This is the three-dimensional structure of the tRNA fMet molecule' scene='Insert optional scene name here' /> |
| - | == | + | ==Function and Interaction with Amino Acid== |
| - | = | + | tRNA fMet is the tRNA used for the initiation of protein synthesis in bacteria. Called an, "initiator tRNA," it is the fist tRNA molecule that enters a bacterial ribosome, specifically at the P site. This is in contrast to all other bacterial tRNAs which enter the A site. The amino acid attached to tRNA fMet is N-formylmethionine, which is the first amino acid assembled into the polypeptide chain during bacterial translation. N-formylmethionine attaches to tRNA fMet on its <scene name='TRNA/Acceptor_cartoon/1'>acceptor stem</scene>. This acceptor stem is a CCA sequence on the 3' end of the tRNA. |
| - | == | + | ==tRNA fMet and Ribosome / mRNA Interaction== |
| - | < | + | Like all tRNA molecules, tRNA fMet is composed of <scene name='TRNA/Fullview_cartoon/1'>four helical stems</scene>. Of these four stems, the <scene name='TRNA/Anticodon_cartoon/2'>anticodon</scene> loop of the tRNA fMet is critical to its function because of how it attaches to the "AUG" initiation codon on the mRNA molecule through base pairing. This binding to the initiation codon requires initiation factor 2 (IF-2) and forms a complex with GTP. This complex is collectively referred to as the 30S initiation complex and is located within the cytoplasm of the cell. At this point, the mRNA molecule has already been bound to the small subunit of the ribosome. As the ribosome translocates down the mRNA strand, additional tRNA molecules enter the ribosome with amino acids that bond with the N-formylmethionine previously attached to tRNA fMet. In this way, tRNA fMet is one of the molecules that begins the process of converting a genetic code to a protein. |
| + | ==Origination of tRNA fMet== | ||
| - | + | tRNA fMet is present as the initiator tRNA in bacteria, but not in eukaryotes or archaeans. Currently, the origin of tRNA fMet remains a mystery among scientists and geneticists. However, because of its presence in only one of the domains of life, there are two possible scenarios for the molecule's origin. It can either be inferred that tRNA fMet originated in bacteria after archaeans diverged from bacteria, or that it originated in the common ancestor of bacteria and archaeans, and then was lost in archaeans after they diverged. tRNA Pro, tRNA Glu, and tRNA Thr all appear to be possible ancestors of the tRNA fMet molecule that is currently used as bacterial initiator tRNA. The reason for switching from these tRNAs to tRNA Met is unclear. Nonetheless, initiator tRNAs themselves are highly conserved across all domains of life, as they are crucial to protein synthesis. | |
| - | + | ==References== | |
| - | == References == | + | |
| - | + | Pierce, Benjamin A. Genetics: a conceptual approach. New York: Freeman, 2012. Print. | |
| + | |||
| + | Bhattacharyya, Souvik. "Evolution of Initiator TRNAs and Selection of Methionine as the Initiating Amino Acid." Tandfonline. RNA Biology, 20 June 2016. Web. 08 Feb. 2017. | ||
| + | |||
| + | "TRNA." TRNA - Proteopedia, Life in 3D. N.p., n.d. Web. 08 Feb. 2017. | ||
Current revision
Contents |
tRNA fMet
|
Function and Interaction with Amino Acid
tRNA fMet is the tRNA used for the initiation of protein synthesis in bacteria. Called an, "initiator tRNA," it is the fist tRNA molecule that enters a bacterial ribosome, specifically at the P site. This is in contrast to all other bacterial tRNAs which enter the A site. The amino acid attached to tRNA fMet is N-formylmethionine, which is the first amino acid assembled into the polypeptide chain during bacterial translation. N-formylmethionine attaches to tRNA fMet on its . This acceptor stem is a CCA sequence on the 3' end of the tRNA.
tRNA fMet and Ribosome / mRNA Interaction
Like all tRNA molecules, tRNA fMet is composed of . Of these four stems, the loop of the tRNA fMet is critical to its function because of how it attaches to the "AUG" initiation codon on the mRNA molecule through base pairing. This binding to the initiation codon requires initiation factor 2 (IF-2) and forms a complex with GTP. This complex is collectively referred to as the 30S initiation complex and is located within the cytoplasm of the cell. At this point, the mRNA molecule has already been bound to the small subunit of the ribosome. As the ribosome translocates down the mRNA strand, additional tRNA molecules enter the ribosome with amino acids that bond with the N-formylmethionine previously attached to tRNA fMet. In this way, tRNA fMet is one of the molecules that begins the process of converting a genetic code to a protein.
Origination of tRNA fMet
tRNA fMet is present as the initiator tRNA in bacteria, but not in eukaryotes or archaeans. Currently, the origin of tRNA fMet remains a mystery among scientists and geneticists. However, because of its presence in only one of the domains of life, there are two possible scenarios for the molecule's origin. It can either be inferred that tRNA fMet originated in bacteria after archaeans diverged from bacteria, or that it originated in the common ancestor of bacteria and archaeans, and then was lost in archaeans after they diverged. tRNA Pro, tRNA Glu, and tRNA Thr all appear to be possible ancestors of the tRNA fMet molecule that is currently used as bacterial initiator tRNA. The reason for switching from these tRNAs to tRNA Met is unclear. Nonetheless, initiator tRNAs themselves are highly conserved across all domains of life, as they are crucial to protein synthesis.
References
Pierce, Benjamin A. Genetics: a conceptual approach. New York: Freeman, 2012. Print.
Bhattacharyya, Souvik. "Evolution of Initiator TRNAs and Selection of Methionine as the Initiating Amino Acid." Tandfonline. RNA Biology, 20 June 2016. Web. 08 Feb. 2017.
"TRNA." TRNA - Proteopedia, Life in 3D. N.p., n.d. Web. 08 Feb. 2017.
