1AQE

CRYSTAL STRUCTURE OF THE Y73E MUTANT OF CYTOCHROME C OF CLASS III (AMBLER) 26 KD

Summary for 1AQE

• Entry DOI: 10.2210/pdb1aqe/pdb
• Descriptor: CYTOCHROME C3, SULFATE ION, PROTOPORPHYRIN IX CONTAINING FE, ... (4 entities in total)
• Functional Keywords: electron transport, octaheme cytochrome, point mutant
• Biological source: Desulfomicrobium norvegicum
• Cellular location: Periplasm: P38554
• Total number of polymer chains: 1
• Total formula weight: 15068.91

Authors

Czjzek, M.,Haser, R. (deposition date: 1997-07-29, release date: 1998-02-04, Last modification date: 2024-11-06)

Primary citation

Aubert, C.,Giudici-Orticoni, M.T.,Czjzek, M.,Haser, R.,Bruschi, M.,Dolla, A.
Structural and kinetic studies of the Y73E mutant of octaheme cytochrome c3 (Mr = 26 000) from Desulfovibrio desulfuricans Norway.
Biochemistry, 37:2120-2130, 1998

PubMed Abstract: A combination of structural, kinetic, and interaction experiments has been used to study the role of a highly conserved aromatic residue, Tyr73, parallel to the sixth heme axial ligand of heme 4 in multiheme cytochrome c3 (Mr = 26 000), also called cytochrome cc3 or octaheme cytochrome, from Desulfovibrio desulfuricans Norway. This residue is expected to be involved in intermolecular electron transfer and protein-protein interaction, since heme 4 is described to be the interaction site between physiological partners. The kinetic experiments show that the Y73E replacement provokes no significant change in the electron-transfer reaction with the physiological partner, the [NiFeSe] hydrogenase, but that the protein-protein interaction between cytochrome c3 (Mr = 26 000) and hydrogenase is strongly affected by the mutation. The aromatic residue does not play a role in maintaining the axial heme ligand in a particular orientation, since the mutation did not affect the orientation of histidine 77, the sixth axial ligand of heme 4. The structural analysis by X-ray crystallography clearly shows that a rearrangement of the charged residues in the vicinity of the mutation site is responsible for the change in protein-protein interaction, which is of an electrostatic nature. Lys22 and Arg66, residues which are located at the interacting surface, are twisted toward the mutated position Glu73 in order to compensate for the negative charge and therefore are no longer accessible for the docking with a physiological partner. Tyr73 has instead a structural function and probably a role in maintaining the hydrophobic environment of the heme 4 cavity rather than a function in the intermolecular electron transfer with the physiological partners.

PubMed: 9485359
DOI: 10.1021/bi971656g

Experimental method

X-RAY DIFFRACTION (2.2 Å)