Question

Transport across the nucleus is carried out by all of the following except?

• A. Caveolins
• B. Local signals
• C. Importins
• D. Rat proteins

Hint:

Three options are real transport machinery; one is a lab reagent term.

Answer 1

The Correct Option is D

Step 1: Movement of molecules in and out of the nucleus happens through the nuclear pore complex and depends on carrier proteins called karyopherins, plus localisation signals on the cargo.

Step 2: Importins are karyopherins that carry proteins into the nucleus by binding their nuclear localisation sequences (NLS); they work with subunits importin alpha and importin beta. Local signals such as the NLS and nuclear export signal direct this traffic. Caveolins, while mainly plasma-membrane proteins, are also described in nucleocytoplasmic shuttling pathways.

Step 3: "Rat proteins" is not a recognised nuclear transport molecule. The phrase refers to recombinant rat proteins used in cell culture, with no role in nuclear import or export.

Step 4: Therefore the exception, the one not involved in nuclear transport, is rat proteins.