Molecular chaperones-
The spontenity folding of protein is not takes place in case of all the proteins. Some proteins need a class of other proteins for a proper folding. The other proteins are called chaperones.
It is present in both prokaryotic and eukaryotic structures. Chaperones were 1st identified in bacteria E.Coli.
1.Hsp 60( 60 kDa) [ GroEL/GroES in E.coli ] Also called chaperonins forms barrel shaped structure.
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The spontenity folding of protein is not takes place in case of all the proteins. Some proteins need a class of other proteins for a proper folding. The other proteins are called chaperones.
It is present in both prokaryotic and eukaryotic structures. Chaperones were 1st identified in bacteria E.Coli.
1.Hsp 60( 60 kDa) [ GroEL/GroES in E.coli ] Also called chaperonins forms barrel shaped structure.
GroEL (Larger heptameric structure with 14 identical residues )HSP60 in E.coli)binds to many unfolded proteins . Interaction with the substrate is based on hydrophobic interactions between surfaces of the substrate and residues of GroEL that are exposed in its central cavity. ATP and protein cap GroES (Smaller heptameric subunit with 7 identiical subunits) binds. ATP hydrolysis occur for release of GroES and the protein molecule. A new unfolded protein molecule can now bind to GroEL.
2.Hsp 70 (70 kDa) It is induced by stress i,e heat shock . Both eukaryotic and prokaryotic.Bind with partially folded polypeptides with exposed hydrophobic regions and prevent aggregation.
The E.coli analogs of HSP70 and Hsp40 are Dna k and Dna J respectively.
Dna J binds to unfolded protein and then to Dna k. Dna J stimulates ATP hydrolysis by Dna k. Dna-k Adp binds tightly to the unfolded proteins.
In bacteria the nucleotide exchange factor Grp E stimulates release of ADP.
ATP binds to Dna k and then the protein dissociates .
Note -Chaperones are used to prevent misfolding and aggregation .
It is necessary in crowded intracellular environment to prevent aggregation .
1.-----------------mediate protein folding .
a.Chaperones
b.Ribosomes
c.Protein itself
d.None of the above
Ans. a
2.Hsp 70 (70 kDa) It is induced by stress i,e heat shock . Both eukaryotic and prokaryotic.Bind with partially folded polypeptides with exposed hydrophobic regions and prevent aggregation.
The E.coli analogs of HSP70 and Hsp40 are Dna k and Dna J respectively.
Dna J binds to unfolded protein and then to Dna k. Dna J stimulates ATP hydrolysis by Dna k. Dna-k Adp binds tightly to the unfolded proteins.
In bacteria the nucleotide exchange factor Grp E stimulates release of ADP.
ATP binds to Dna k and then the protein dissociates .
Note -Chaperones are used to prevent misfolding and aggregation .
It is necessary in crowded intracellular environment to prevent aggregation .
1.-----------------mediate protein folding .
a.Chaperones
b.Ribosomes
c.Protein itself
d.None of the above
Ans. a
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