This is rather up to you, the teacher. The main thing is the one big loop
from each subunit to the other that gets very close to the other monomer's
active site.
It is worth mentioning that the serine in the tip of that loop interacts with
the active site residue Lys-12 of the other subunit. Such interactions can help
with cooperativity, but I don't know if that also happens in TIM.