BIOINORGANIC CHEMISTRY A Short Course Second Edition

462 IRON-CONTAINING PROTEINS AND ENZYMES

The second copper ion, Cu 2 , is ligated to the N δ of his137 and the N ε of his139.
The dinuclear copper center ligands are shown as stick fi gures in Figure 7.51.
His137 and his139 are highly conserved in pMMO and AMO from a number
of organisms. His33 has hydrogen bonds to the side chain of glu35 as has his139
to the carbonyl oxygen of gly152. Both glu35 and gly152 are also highly
conserved.
The 1PDB: 1YEW pmoA and pmoC subunits reside mainly in the mem-
brane. Subunit pmoA includes residues 7 – 244 is colored yellow in Figure 7.51.
The pmoA subunit contains seven TM α - helices, some of which pack against
the TM helices from pmoB. Two pmoA helices face the trimer center hole and
interact with counterparts from the other two protomers (not shown in Figure
7.51 ).
The subunit pmoC, colored red in Figure 7.51 , is comprised of fi ve TM α -
helices that are oriented approximately parallel to the membrane normal and
to each other. A single zinc metal ion, in a distorted tetrahedral coordination
sphere, has been modeled within the membrane. Conserved amino acid resi-

Figure 7.51 Particulate MMO, pMMO (PDB: 1YEW). Visualized using Cambridge-
Soft Chem3D Ultra 10.0 with notations in ChemDraw Ultra 10.0. (Printed with permis-
sion of CambridgeSoft Corporation.) (See color plate)

Zinc ion

Dinuclear Copper

Ion

Mononuclear

Copper Ion

PDB: 1YEW

pmoB: cyan

pmoA: yellow

pmoC: red