We have some of these alpha chains. And right about here at the interface between the red regulatory chain and this orange catalytic chain, we're going to find a zinc atom. And that zinc atom interacts with the Sistine residues with four cysteine residues. And that basically amplifies it makes better the interaction between the orange chain, the catalytic chain and the red chain that regulatory chain. So each R regulatory subunit contains a zinc domain that contains the zinc metal atom that interacts with the C subunit, the catalytic subunit. So again, each one of these red regulatory chains in the dimer interacts with one of these catalytic chains in that catalytic trimer via this metal atom that is present within the end portion, the interface section of each one of these regulatory chains.