Question

9. Which of the following statements about cytosolic proteins is correct?

1. They can be stabilized by disulfide bonds between appropriately located cysteine residues and can be phosphorylated on serine residues.

2. None of these statements are correct

3. They can be phosphorylated on serine residues

4. They can be stabilized by disulfide bonds between appropriately located cysteine residues.

Answer 1

Answer- 1) They can be stabilized by disulfide bonds between appropriately located cysteine residues and can be phosphorylated on serine residues.

Reason- Cytosolic protein are synthesized by ribosomes in cytoplasm. Disulfide bonds present the in proteins, are formed between the thiol groups of cysteine residues by the process of oxidative folding. It stabilizes proteins by reducing the entropy of the denatured state. Phosphorylation usually occurs on serine, tyrosine and histidine residues in a eukaryotic proteins.Thus this addition of a PO4 molecule to the R-group of an amino acid residue turns a hydrophobic portion of a protein into hydrophilic portion.