t rna structure

1. SECONDARY STRUCTURE OF t RNA CLOVER LEAF MODEL
Bharatesha.S
IV semester
Molecular biology Dept.
Yuvaraja’s college
2012-13
Guided by:
Chandrakanth .R
Molecular biology Dept.

2. CONTENT:
 INTRODUCTION
 ABOUT RNA
 TYPES OF RNA
 UNIQUE CHARACTERISTICS OF t RNA
 CLOVER LEAF MODEL
 3D STRUCTURE OF t RNA
 TRANSLATION
 CONCLUSION
 REFERENCE

3. INTRODUCTION:
 In the cloverleaf model, the inverted sequences form four double-helical
segments. The two ends of the molecule form the amino acid arm or
acceptor stem. A single strand sequence - CCA - protrudes from the 3’-end of
the molecule.
 The terminal A is coupled to the amino acid during amino acid activation.
The next arm, moving clockwise, is the TPsiC arm. This arm got its name
from the occurrence of the sequence TPsiC in almost all tRNA
(Psi, pseudouridine, is a modified U). In eukaryotic initiator tRNAs, TPsiC is
substituted for by AUC or APsiC.
 The next arm is the variable arm which may contain between 4 and 21
nucleotides. Adjacent to the variable arm is the anticodon arm with the three
nucleotide anticodon which pairs with the codon during translation.
 The last arm of the tRNA is the DHU-arm named after the occurrence
of dihydrouridine in all tRNAs.

4. RNA is polymeric nucleic acid of four monomeric
ribonucleotides. Each ribonucleotide contains a
pentose sugar (D-ribose), a molecule of phosphate
group and nitrogen base. The nitrogen base of RNA
are two puriens, adenine and guanine, and two
pyrimidines, cytosine and uracil.
RNA molecule may be either single stranded or
double stranded but not helical like DNA.
In the polynucleotide strand of RNA, the ribose and
phosphoric acids of nucleotides remain linked by
phosphodiester bonds.
Genetic RNA undergoes RNA- dependent-RNA
synthesis whereas each genera of non-genetic RNA as
DNA dependent replication.
RNA is highly unstable and it can undergo mutation
easily.
ABOUT RNA:-

5. Types of RNA:-
Messenger RNA (mRNA) is synthesized from a gene segment of DNA
which ultimately contains the information on the primary sequence of
amino acids in a protein to be synthesized. The genetic code as translated
is for m-RNA not DNA. The messenger RNA carries the code into the
cytoplasm where protein synthesis occurs.
Ribosomal RNA:
In the cytoplasm, ribosomal RNA (rRNA) and protein combine to form a
nucleoprotein called a ribosome. The ribosome serves as the site and
carries the enzymes necessary for protein synthesis. The ribosome
attaches itself to m-RNA and provides the stabilizing structure to hold all
substances in position as the protein is synthesized.
Transfer RNA:
Transfer RNA (tRNA) contains about 75 nucleotides, The tRNA reads
the code and carries the amino acid to be incorporated into the
developing protein.
In this example, the tRNA anticodon (AAG) reads the codon (UUC) on
the mRNA. The UUC codon codes for phenylalanine which is attached
to the tRNA.

6. Unique characteristics of Transfer RNA:
It is a relatively small molecule
of 75 to 90 ribonucleotides.
The ratio of A:U and G:C are
near unity.
All t RNA molecules have a
tertiary structure.
A number of “ unusual”
nucleotides are found in t RNA.

7. Robert Holley (1965)and his colleagues reported the complete
nucleotide sequence of alanine t RNA of yeast. Holley received
the Nobel prize in 1968.
TRANSFER RNA STRUCTURE:-

8. In order to understand the structure-function relationship of t RNA , its
3D structure was worked out by the help of X-ray crystallography study.
 A. Klug, the Nobel laureate of 1982, has contributed much to the TDS
of t RNA.
 S.H,Kim(1973) proposed a most acceptable TDS model of t RNA of
yeast cell. According to Kim, TDS of t RNA takes the shape of letter L
with a thickness of 10A.
3D STRUCTURE OF TRANSFER RNA:-

9. ROLE OF TRANSFER RNA IN TRANSLATION:

10. CONCLUSION:
 t RNA is special compare to other
RNA because it occurs in double
stranded structure.
 t RNA plays a major role during
translation process.
 Transfer RNA will be a interesting
topic in the field of research.

11. REFERENCE:
 Agarval.V.K. & Verma.P.S. 1st
edition(2009), molecular biology,
S.Chand publication, new Delhi,
392pp.
 Smith 1983.principles of biochemistry.
Mc Graw hill,483pp.