BIOINORGANIC CHEMISTRY A Short Course Second Edition

CYTOCHROMES c 421

Conformational changes are found for the ferrocytochrome c hemes as well
when the PDB: 1LC1 (30% ACN solution) and PDB: 1GIW (aqueous solu-
tion) structures are compared. These are most evident for the propionate
moieties, especially those involving the propionate group attached to heme
pyrrole ring A (the propionate - 7 in terminology of reference 120. (See Figure
7.32 for the nomenclature used for c - type heme groups.) The reference 120
authors believe that this may be due to the loss or movement of water mole-
cule 125. This cannot be confi rmed from the PDB: 1LC1 visualizations
because the water molecules are not included in the Protein Data Bank data.
Sivakolundu and Mabrouk also compare the PDB: 1LC1 ferrocytochrome
Fe(II) c X - ray structure with the X - ray crystallographic structure of ferricyto-
chrome Fe(III) c crystallized at low ionic strength (PDB: 1CRC)^122 and with
the X - ray crystallographic structure of ferricytochrome c complexed with a
physiological binding partner cytochrome c peroxidase, CCP (PDB: 2PCB).^123
They fi nd that the secondary structures are essentially the same and show only
minor differences in loop domains. The orientation of the iron ion ligand his18
is quite similar in all structures, whereas all structures show differences in the
orientation of the heme proprionate - 6 group (attached to pyrrole ring D). The

Figure 7.34 Two horse cytochrome c molecules, (PDB: 1LC1, in various colors as
described in the text, and PDB: 1GIW in green). Visualized using The PyMOL Molecu-
lar Graphics System and ChemDraw Ultra, version 10.0. (Printed with permission of
Delano Scientifi c, LLC and CambridgeSoft, Corporation.) (See color plate)

lys8

lys86, 87

lys72

lys60

his33

PDB: 1LC1, colors

PDB: 1GIW, green

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