Transport RNA (tRNA)

. The nametRNA (transfer RNA) is a
molecule
protein in protein synthesis. There are more than 100 tRNA molecules, each carrying an
amino acid
, which can be transported to the nucleoprotein body for protein synthesis. tRNA is the smallest molecular weight of a class
nucleic acid
, composed of 70 to 120
nucleotides
, a variety of tRNA in the first structure, or in the second and third structure have some common characteristics. TRNA contains 10% to 20% of the rare base (rare bases), such as: methylated pyridine mG, mA, dihydrurialine (DHU), secondary jaundice and so on. In addition, tRNA contains some rare nucleosides, such as thymus nucleosides, pseudourethyridine nucleosides (Ψ, pseudouridine, etc. Thymosin is generally present in
DNA
, where the glycoside bond is formed between five carbon atoms in the ring and one bit of carbon atom in the carboysine ring, not in the hypouretic nucleoside.nucleotides in tRNA molecules form multiple local double helix structures through complementary base pairings, and regions that do not form double helixes form so-called rings and . All tRNAs found can present this so-called clover leafpattern secondary structure shown in Figures 15-14. In this structure, the first ring from the end of the 5' is the DHU ring, characterized by dihydroureacine, and the second ring is an anti-cocoide subcycle, the three bases in the middle of the ring can form a base complementary pair with the triplet codon in mRNA, forming the so-called anticodon, in protein synthesis to interpret the codon, the correct amino acids into the synthesis site The third ring is a TΨ-ring, characterized by thymus nucleosides and false urinary glycosides, and between the anti-cryptic sub-ring and the TΨ-ring, there is often a , consisting of several or even more than twenty nucleotides, all tRNA3' ends have the same CCA-OH structure, tRNA transported amino acids are connected at this end. (Figure 15-14A) . Figure 15-14 TRNA secondary and third-level structure A. secondary structure (a anti-cryptographic ring and anti-password) B. third-stage structure (digital display of possible non-possible non-possible nucleotide pair interaction)through structural analysis methods such as X-ray diffraction, the common discovery of tRNA The three-stage structure is inverted L-shaped (Figure 15-14B), where the amino acid arm containing CCA OH at the end of the 3' is located at one end, the anti-password sub-ring is located at the other end, and the DHU ring and TΨ ring are on one side of the secondary structure, but are adjacent to each other in the third structure. The three-stage structure of tRNA is maintained mainly by relying on various hydrogen bonds formed between nucleotides. The nucleotide sequence and length of various tRNA molecules vary greatly, but their three-stage structures are similar, suggesting that this spatial structure is closely related to the function of tRNA.
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