Question

Lysosomal targeting of proteins involves recognition of

• A. N-terminal signal peptide alone
• B. mannose phosphorylated at 6\textsuperscript{th} carbon in N-linked oligosaccharide
• C. KDEL sequence at the C-terminus
• D. dilysine motifs in the internal sequence of the protein

Hint:

The KDEL sequence is a common signal that helps proteins get targeted to the lysosome for degradation or recycling.

Answer 1

The Correct Option is B

Step 1: Understanding lysosomal targeting.
Proteins destined for the lysosome are often tagged with specific signals, which help them get recognized by the transport machinery that directs them to the lysosome. The KDEL sequence at the C-terminus is a well-known signal for this purpose.

Step 2: Analyzing the options.
(A)N-terminal signal peptide alone: This is incorrect because the N-terminal signal peptide is typically involved in targeting proteins to the endoplasmic reticulum (ER), not specifically to the lysosome.
(B)mannose phosphorylated at 6\textsuperscript{th carbon in N-linked oligosaccharide:} This refers to a tagging mechanism for lysosomal proteins, but it's not the primary signal involved in the transport to lysosomes.
(C)KDEL sequence at the C-terminus: Correct — The KDEL sequence is a key signal for targeting proteins to the lysosome.
(D)dilysine motifs in the internal sequence of the protein: Dilysine motifs are involved in ER retention, not lysosomal targeting.

Step 3: Conclusion.
The correct answer is (C)KDEL sequence at the C-terminus, as it is the specific sequence recognized for lysosomal targeting.