structure of trna

1. Structure of tRNA
SUBMITTED BY :-MAYUR PANKHI SAIKIA
DEPARTMENT:-BIOSCIENCE
COLLEGE:-ASIAN INSTITUTE OF MANAGEMENT AND TECHNOLOGY

2. Acknowledgement
 I would like to express my sincere respect and gratitude to Dr Niren Deka Sir (The
principal of Aimt),Dr Monalisha Saikia Borah Mam (HoD of Bioscience Department
and also our class mentor ) and also the other faculties under, whose guidance I
am able to successfully prepare this presentation.

3. Contents
 Introduction
 Structure of tRNA
Primary structure.
Secondary structure
Tertiary structure
 Functions of tRNA

4. t-RNA
 t-RNA (transfer RNA ) is also named as S-RNA (soluble RNA).
 t-RNA is a family of nearly 60 small sized ribonucleic acids.
 10-15% of total cellular RNA is t-RNA.
 T-RNAs are small molecules with about 74-95 nucleotides.
 Molecular weight – nearly 25,000- 30,000 Dalton.
 T-RNA s are made up of a single stranded polynucleotide chain.

5. Structure of t -RNA
 It consists of three types of structure.
1. Primary structure- linear sequence of nucleotides.
2. Secondary structure- Clover leaf model
3. Tertiary structure- 3D structure of tRNA ,Lshape,Helix stacking.

6. Primary Structure
• Linear sequence of nucleotides is 60-90 long but most commonly 76.
• Three of the nucleotides makes the anticodon

7. Secondary Structure
• Robert Holley proposed the
clover leaf model for the first
time in 1968.
• It is a two dimensional
description of the tRNA .

8. • Double helical(both 5’
and 3’ ends of tRNA).
At 3’ end , 5’CCA 3’
protudes with OH at
the tip.
Site for attachment of
amino acid.

9. • DHU or D arm- This arm consists of stem and
loop with unusual pyrimidine nucleotide
dihydrouracil.
• 4bp with stem with a loop containing
dihydrouridine.
• Recognition site for the specific enzyme
aminoacyl-tRNA synthetase that activates the
amino acid.
• Play an important role in the stabilization of
tRNAs tertiary structure.

10. • This arm is known as Thymine
pseudouridine cytosine where
pseudouridine is unusual base.
• This arm also consists of stem and
loop.
• Stem contains 5 base pairs
outermost of which is C-G.Loop
contains 7unpaired nucleotides.
• The loop contains a ribosome
recognition site.

11. • This arm also contains stem and loop.
• Stem contains 5 base pairs and loop
(called as anticodon loop or loop II )
contains 7 unpaired nucleotides
• Out of these 7 unpaired nucleotides
the middle three form anticodon.
• Anticodon recognizes an codon on the
mRNA and binds to it.

12. Variable arm
 The variable arm is between the anticodon n the T loop.
 This arm is very short so it looks quite different from the other arms of the
molecule.
 May present or absent, it depends on species.
 The length of the variable arm is important in the recognition of the aminoacyl
tRNA synthetase for the tRNA.
 tRNAs are called class I if they lack itn class 2 if they have it.

13. Tertiary Structure:-3D structure
 L-Shaped structur
1. Acceptor arm and T arm form extended helix.
2. Anticodon stem and D-loop stem form extended helix.
3. D-loop and T – loop align together.
4. Both extended helix align at right angles.

14.  Stability of L –structure.
Tertiary structure of t-RNA us produced by
hydrogen bonding –
Between N bases
. Between N bases and ribose
phosphate backbone.
Between ribose phosphate backbone

15. Functions of tRNA
.
 Helps in recognition of aminoacyl-tRNA synthetase enzyme .
 Picks up specific amino acid from cytoplasm and carries to site of protein
synthesis.
 Attach itself to ribosome in accordance with sequence specified by mRNA.
 Transmit amino acid to polypeptide chain.
 Participate in non protein synthetic processes such it act as a primer during
reverse transcriptase in retroviruses.
 tRNA act as a Enzyme Inhibitor
Eg:-Inhibits E.coli endonuclease I

16. 
Thank you