In: Biology
give detailed answers
1. what is the difference between shine Dagarno and Kozak sequence ?
2. discuss ribosomal components
Ribosomal Binding Site (RBS):
This site, located at the 5' untranslated region (UTR) of the mRNA transcript, regulates protein synthesis based on its sequence and structure.
There are two consensus sequences, named Kozak and Shine
Dalgarno (after their discoverers), which are known to facilitate
efficient translation in Eukaryotes and Prokaryotes
respectively.
Name |
Type of Organism |
Description |
Kozak Sequence |
Eukaryote |
Preferred sequence context which allows effective ribosomal
binding at initiation site. The favored context is: |
Shine Dalgarno (SD) Sequence |
Prokaryote |
The SD sequence is complementary to the 3' end of the 16S rRNA.
Its consensus sequence is 5'-UAAGGAGG-3' which is followed by an
initiation codon, most commonly AUG. (About 8% of start sites use
GUG, whereas UUG and AUU are rare initiators present in
autogenously regulated genes). The optimal spacing between the SD
sequence and the start codon is 8 nt, but translation initiation is
severely affected only if this distance is reduced below 4 nt or
increased above 14 nt. [Shine, J. and Dalgarno, L. (1975) Eur. J.
Biochem. 57, 221.] |
Ribosomes:
Components:
The ribosome is a complex molecular machine, found within all living cells, that serves as the site of biological protein synthesis(translation).
Ribosomes link amino acids together in the order specified by messenger RNA (mRNA) molecules.
Ribosomes consist of two major components:
the small ribosomal subunits, which read the RNA and
the large subunits, which join amino acids to form a polypeptide chain.
Each subunit comprises one or more ribosomal (rRNA) molecules and a variety of ribosomal proteins (r-protein or rProtein).
The ribosomes and associated molecules are also known as the translational apparatus.