The amino acid sequences that target proteins to chloroplasts, mitochondria and

Question

The amino acid sequences that target proteins to chloroplasts, mitochondria and nuclei have the following property in common:

A. They are located near the amino terminus of the precursor proteins

B. They are rich in hydrophobic amino acids

C.When added in the proper context, they are sufficient to direct the targeting of a foreign proteins into the respective organelles

D. They are all removed by proteolysis after transport is completed

The nuclear transport receptor can bind to:
A. FG nucleoporins.

B. Ran·GTP

C. basic nuclear localization signals in cargo proteins.

D. all of the above

Which of the following is a lectin?

A. BiP.

B. calnexin.

C. PDI.

D. prolyl isomerase.

Explanation / Answer

1. Answer Option C. When added in the proper context, they are sufficient to direct the targeting of a foreign proteins into the respective organelles

2. Answer. Option B .Calnexin

Lectins are glycoproteins which are of plant origin. Lectins bind specifically to particular carbohydrates.

Calnexin are lectin chaperons located in the Endoplasmic reticulum which bind specifically to N-linked glycoproteins that ensures protein folding and quality control.

BiP is binding immunoglobulin protein, a molecular chaperon present in the ER binds specifically to newly synthesised proteins. PDI is protein disulfide isomerase located in ER which forms disulphide crosslink between two cysteine residues. Prolyl isomerases are enzymes which catalyse cis-trans isomerisation of peptide bonds playing a role in protein folding.

BiP, PDI and prolyl isomerase interact with amino acids during protein folding. Calnexin bind to specific carbohydrate during protein folding.

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