What is GST-Nga recombinants?

Question

I'm reading a study on NAD-glycohydrolase in streptococcal strains (one of the bacteria responsible for necrotizing fasciitis), and there are lots of terms that I dont understand. Most of them I google, but for this one, i couldnt find any definition of explanation. A source would be awesome (just so i can read more on it if i get stuck). thanks!

What is 'GST-Nga recombinant'?

Sentence: "Analysis using GST-Nga recombinants revealed that nga alleles of representative older strains encode inactive Nga" (Nga = NADas = NAD-glycohydrolase).

Answer 1

They're talking about recombinant protein.

To study how proteins behave, function and bind to other proteins sometimes you need a lot of one particular protein.  One way to do this is to express it recombinantly using bacteria.  

GST is an enzyme called "Glutathione S Transferase".  It's a soluble protein that will bind to a protein called Glutathione that can be immobilized on a bead.  

So what people do is take the DNA from their protein of interest, subclone (fuse the DNA in frame so you have GST-DNA of your protein) it to the GST enzyme and express the whole thing in bacteria.  The bacteria act like protein factories and make a whole ton of your GST fusion protein.

Then you simply break open the bacteria and use the Glutathione beads to pull your fusion protein out of the mix of bacterial proteins (this is called affinity purification).  

Now you have a ton of protein that you can use for activity assays or whatever.  

It sounds like they just made a bunch of GST-Nga from different strains (of whatever) and tested them one by one for activity.  

I do this fairly routinely in the lab I work in so if you have questions email me.