Structural highlights
, pdb structure 3fhi[1], is shown with the catalytic unit's small lobe in gray and large lobe in tan, and the regulatory unit in light blue.
The . Here the catalytic unit's residues which do interact with the regulatory unit are represent with halos and ball-and-stick. The residues from exon 1 of the catalytic unit are labelled by residue index. Note that the last three residues from exon 1 (residues # 13-15) are the only amino acids from the first exon of the catalytic unit that were included in this crystal structure. As seen in the structure, the exon 1 residues are over 30 angstroms from the regulatory unit - too far to bind.
The crystal structure for the tetromeric holoenzyme, 3tnp, supports the above observation. There is no interaction between , shown with halos, to the regulatory units, shown in green and purple.
In addition, the exon 1 residues are also - a second regulator/inhibitor of the catalytic unit, as well. The exon 1 residues are distant from all regulatory units, both the pka regulator unit as well as the pki unit .
This is also obvious from the pdb structure for the , 1atp[2].
