• Prosthetic group features
• Soluble cytochrome b₅₆₂ in SWISS­PROT/TREMBL
• Soluble cytochrome b₅₆₂ in alignment databases
• Soluble cytochrome b₅₆₂ in 3­D databases
• References

Haem type	Haem iron coordination	Axial iron ligands	Formal iron oxidation/spin states
Haem b	Hexacoordinate	NHis; SMet	FeII (S=0); FeIII (S=1/2)

Cytochromes b (cyt b) can be defined as electron­transfer proteins having one or two haem b groups, noncovalently bound to the protein. The fifth haem iron ligand is always provided by a histidine residue. Cyt b possess a wide range of properties and function in a large number of different redox processes [1].

A number of cytochromes with very different sequences and haem coordination centres share a common 3­D structure, namely a four­­helix left­twisted antiparallel bundle [2]. This group includes soluble cyt b₅₆₂, cyt b₅₅₇ (bacterioferritin), and Class II cyt c. Although soluble cyt b₅₆₂ from the periplasm of Escherichia coli has this characteristic chain fold, its sequence bears no similarity to the other four­­helix bundle cytochromes. The protein consists of four nearly parallel ­helices; the haem group is inserted between the helices near one end of the molecule with one heme face partially exposed to solvent (see Figure 256B). Histidine and methionine provide the fifth and sixth haem ligands [3].

Soluble cytochrome b₅₆₂ in SWISS­PROT/TREMBL

C562_ECOLI

Soluble cytochrome b562 precursor; Escherichia coli

Soluble cytochrome b₅₆₂ in alignment databases

Protein Superfamily	Pfam	LPFC 3­D alignment
00018; cytochrome b562	-	-

PDB	scop	BSM	RELI Base	Header	¹
1apc¶	1apc¶	1apc¶	1apc	Cytochrome b562 (apo form); Escherichia coli	MS5IB4
256b	256b	256b	256b	Cytochrome b562 (oxidised) (complex with sulphate); Escherichia coli	-

¹ Macromolecular Structures abstract. Full text is available to BioMedNet Members

References

1. Kiel, J.L. (1995) Type­b Cytochromes: Sensors and Switches. CRC Press, Boca Raton.
2. Moore, G.R. (1991) Bacterial 4­­helical bundle cytochromes. Biochim. Biophys. Acta 1058, 38-41.
3. Mathews, F.S., Bethge, P.H. and Czerwinski, E.W. (1979) The structure of cytochrome b₅₆₂ from Escherichia coli at 2.5 Å resolution. J. Biol. Chem. 254, 1699-1706.

Bibliography on structural studies of soluble cytochrome b562