Question:
Most soluble Endoplasmic Reticulum-resident proteins have a C-terminal motif/tag viz. KDEL. The sequence of amino acids in this motif/tag is ?
Most soluble Endoplasmic Reticulum-resident proteins have a C-terminal motif/tag viz. KDEL. The sequence of amino acids in this motif/tag is ?
Show Hint
Match the single-letter codes to their amino acids:
K = Lysine
D = Aspartic acid
E = Glutamic acid
L = Leucine
This KDEL sequence serves as a retrieval signal for ER-resident proteins.
K = Lysine
D = Aspartic acid
E = Glutamic acid
L = Leucine
This KDEL sequence serves as a retrieval signal for ER-resident proteins.
Updated On: Aug 7, 2026
- Lysine-Aspartic acid-Glutamic acid-Leucine
- Leucine-Aspartic acid-Glutamic acid-Lysine
- Lysine-Glutamic acid-Aspartic acid-Leucine
- Leucine-Glutamic acid-Aspartic acid-Lysine
Show Solution
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The Correct Option is A
Solution and Explanation
Step 1: Understanding the Concept:
Proteins synthesized in the secretory pathway are targeted to specific subcellular compartments using sorting signals.
Soluble proteins destined to reside in the lumen of the endoplasmic reticulum (ER) contain a specific C-terminal retrieval signal that prevents their secretion.
Step 2: Detailed Explanation:
The KDEL target motif is a tetrapeptide sequence located at the C-terminus of soluble ER-resident proteins (such as BiP and protein disulfide isomerase).
These letters represent the standard single-letter codes for specific amino acids:
- K represents Lysine
- D represents Aspartic acid
- E represents Glutamic acid
- L represents Leucine
Therefore, the sequence of amino acids in the C-terminal KDEL tag is Lysine-Aspartic acid-Glutamic acid-Leucine.
If these proteins escape from the ER to the Golgi apparatus, they bind to KDEL receptors present in the cis-Golgi membrane.
This binding triggers retrograde transport of the protein-receptor complex back to the ER via COPI-coated vesicles, preserving the functional protein pool within the ER lumen.
Step 3: Final Answer:
The amino acid sequence of the KDEL motif is Lysine-Aspartic acid-Glutamic acid-Leucine, which corresponds to Option (A).
Proteins synthesized in the secretory pathway are targeted to specific subcellular compartments using sorting signals.
Soluble proteins destined to reside in the lumen of the endoplasmic reticulum (ER) contain a specific C-terminal retrieval signal that prevents their secretion.
Step 2: Detailed Explanation:
The KDEL target motif is a tetrapeptide sequence located at the C-terminus of soluble ER-resident proteins (such as BiP and protein disulfide isomerase).
These letters represent the standard single-letter codes for specific amino acids:
- K represents Lysine
- D represents Aspartic acid
- E represents Glutamic acid
- L represents Leucine
Therefore, the sequence of amino acids in the C-terminal KDEL tag is Lysine-Aspartic acid-Glutamic acid-Leucine.
If these proteins escape from the ER to the Golgi apparatus, they bind to KDEL receptors present in the cis-Golgi membrane.
This binding triggers retrograde transport of the protein-receptor complex back to the ER via COPI-coated vesicles, preserving the functional protein pool within the ER lumen.
Step 3: Final Answer:
The amino acid sequence of the KDEL motif is Lysine-Aspartic acid-Glutamic acid-Leucine, which corresponds to Option (A).
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