Question

1a.Which of the following protein maintains Ran in a GTP bound form (Ran-GTP) and where is this protein localized?
   Rab GEF; nucleus
   Ran GEF; nucleus
   Ran GEF; cytosol
   Rab GAP; cytosol
   Ran GAP; nucleus

1b.Select the true statement about intracellular transport/trafficking:
   Signal sequences are not required for most protein transport
   Gated nuclear pore complex allows free diffusion of some molecules
   protein transport into the mitochondrial matrix is only driven (provide energy) by the        Hsp70 ATPase
   mRNA leaves the nucleus only by passive diffusion
   Molecules move from smooth ER to Golgi through transmembrane transport

1c.What is the name of the protein complex that arrest protein translation until the ribosomes associate with the protein translocator on the ER membrane?
   The SRP complex
   The proteasome complex
   The Sec61 complex
   The Tim/Tom complex
   The SNARE complex

Answer 1

1a. Ran exists in two forms in the cell. One is GTP-bound form and other is GDP bound form. Ran's GTP activity is activated through interaction with Ran GTPase activating protein (RanGAP),which is bound to nuclear envelope.So option 5 is correct.

1b. Signal sequences are needed for protein transport.Protein transport into mitochondrial matrix is driven by both ATP hydrolysis and membrane potential. mRNA leaves nuclear pore complex by cell signalling. Only water and glucose leave by osmosis or diffusion.

The statement which is true is( option 5) that proteins are transported from smooth ER to golgi by transmembrane transport, where carriers or budding of vesicles happen and the protein is transported.

1c. SRP complex arrests protein translation until the ribosomes associate with the protein translocator