Question

Track the movement of A) PFK and B) sodium-potassium pumps from the organelle that initiates their synthesis to their final location. Note that one pathway is extremely simple, but the other involves more organelles. Also note that you are only tracking the movement of the protein, so start with the initiation of translation.

Answer 1

1. Track movement of PFK.

PFK or phosphofructokinase is an enzyme that converts fructose-6-phosphate to fructose-1,6-bisphosphate with the help of ATP. PFK catalyses this reaction in cytoplasm of cells. As a protein it is synthesized in cytoplasm and its destination is also cytoplasm. So the movement can be tracked using CFP (Cyan fluorescent protein)  tagged to PFK. So after the translation of the CFP tagged PFK, the localization can be tracked under fluorescent microscope.  

2. Track movement of sodium-potassium pump.

Sodium-potassium pump is a heterodimer consisting of two alpha and two beta subunits. While the alpha subunit is responsible for ion transport the beta subunit is required for the assembly of the complex. Alpha and beta subunits are the products encoded by different genes on different chromosomes, so there mRNA has to be translated separately and then the subunits assemble. As Sodium-potassium pump is destined for the plasma membrane, the synthesis of both alpha and beta subunits starts on endoplasmic reticulum,ER (as it happens for other secretory proteins). Assembly of alpha and beta subunits of Sodium-potassium pump occours in ER. So following their synthesis and assembly in ER, next they move to golgi where they are packaged into vesicles and finally transported to plasma membrane where the vesicles fuse with the plasma membrane to deliver the cargo or in this case the assembled Sodium-potassium pump .

So in this case two different proteins are synthesized and coming together after a certain point of time or they co-localize with one another. Here alpha and beta subunits can be tagged with different fluorophores, say alpha subunit with RFP (red fluorescent protein) and beta with GFP (Green fluorescent protein). Now when they are synthesized as separate proteins you will see red color for alpha and green color for beta subunit. Once they co-localize you will see a yellow color (as simultaneous fluorescence of primary colors red and green gives rise to secondary color yellow) indicating that now alpha and beta subunits have assembled.