Clover leaf model of t-rna

Clover leaf model of t-rna -

• Transfer RNA
   (tRNA) directly engaged in protein synthesis (Translation). They carry the amino acids  and hand them over to the growing polypeptide chains. 
• The anticodon is a trinucleotide sequence in tRNA which is responsible to recognize the codon (complementary bases) of the  mRNA for protein synthesis.The amino acid is covelently bound to t-RNA at the 3'-end.
• Two or more different t-RNA that are specific for same amino acid are termed isoaccepting t-RNA.

•  Cloverleaf model of tRNA (Secondary structure ) is a model that depict the molecular structure of tRNA.-
• The acceptor stem is a 7 to 9base pair (bp) stem made by the base pairing of the 5'terminal nucleotide with the 3'-terminal nucleotide (which contains the CCA 3'terminal group used to attach the amino acid). 

• The amino acid loaded onto the tRNA by  enzyme aminoacyl tRNA synthetases.tRNA is charged to form aminoacyl-tRNA by forming an ester link from the  3'OH group of the adenylic acid at the end of the acceptor arm to the COOH group of the amino acid.The COOH group of the amino acid is linked  covalently to the 3'-hydroxyl group on the CCA tail.  

• The D arm is a 4 to 6bp stem ending in a loop that often contains dihydrouridine.
• The anticodon arm is a 6bp stem whose loop contains the anticodon. The t-RNA 5'-3' primary structure contains the anticodon but in reverse order.
• The first anticodon base, or wobble-position, is sometimes modified to inosine (derived from adenine),pseudouridine or lysidine (derived from cytosine).
• An arm of tRNA is one of the four (or in some cases five) stem-loop structures that make up the secondary structure.
• The acceptor arm of tRNA is a short duplex that terminates in the CCA(cytosine-cytosine-adenine) sequence in the 3' end to which an amino acid is linked.
• The extra arm of tRNA lies between the TψC and anticodon arms. It is the most variable in length in tRNA, from 3-21 bases.
• The t-RNA  has a sequence of 74-95 bases that folds into a clover-leaf secondary structure with four constant arms (and an additional arm in the longer tRNAs).

2-D STRUCTURE OF t-RNA

 Image source credit- http://hyperphysics.phy-astr.gsu.edu/hbase/organic/trna.html

3-D STRUCTURE OF t-RNA

  Image  source - http://text.c.utokyo.ac.jp/larlge_fig/fig03_11b.html

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