Transketolase

PDB file 1NGS

This file depicts Transketolase with bound erythrose-4-phosphate, an acceptor of the 2-C fragment transferred by this enzyme. This structure was solved by Nilsson, Lindquist, & Schneider, 1997.

Suggested display options:

To distinguish the 2 copies of the protein, color chain.


Select
hetero-ligand, display as sticks or ball & stick, and color CPK.
Identify the thiamine pyrophosphate (TPP) and the erythrose-4-phosphate substrate,

Locate the carbon atom in the thiazole ring of TPP, between N (blue) and S (yellow), that tends to dissociate a proton to become a reactive carbanion.
Note the conformation of TPP & the position of the amino N of the aminopyridine moiety that is thought to accept a proton from the acidic carbon in the thiazolium ring.

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Find the glutamate residue, near the aminopyridine ring, which promotes the proton transfer.
Note the position of the reactive carbon on TPP relative to the aldehyde at carbon #1 of the substrate erythrose-4-P. 

Then select protein, display as spacefill with color chain.
Question:
Are TPP and erythrose-4-P buried or at the enzyme surface?
Does each copy of the enzyme in the dimer have its own active site independent of the other subunit? 


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