TSRI's main web site PROMISE mirror at TSRI Metalloprotein DB site Created: 17 December 1996
Last modified: 22 October 1998

Haemerythrin family
Binuclear iron centre Iron ligands Formal iron
oxidation states
Fe1
Fe2

Hexacoordinate + Pentacoordinate
3 × NepsilonHis
2 × NepsilonHis
2×FeII;

FeIIFeIII
µ­eta1:eta1­OdeltaAsp;

µ­eta1:eta1­OepsilonGlu;

µ­OH

2×Hexacoordinate
3 × NepsilonHis
2 × NepsilonHis;

OOH-

2×FeIII
µ­eta1:eta1­OdeltaAsp;

µ­eta1:eta1­OepsilonGlu;

µ­O

The haemerythrin family (Class III diiron-carboxylate proteins) includes the nonhaem dioxygen (O2)­binding proteins haemerythrin and myohaemerythrin [1]. Haemerythrin (Hr) has been isolated from the blood of marine invertebrates (annelids, brachiopods and sipunculids). Hr typically exists as an homooctamer or heterooctamer composed of alpha­ and ß­type subunits of 13-14 kDa. Myohaemerythrin (Mr) is a monomeric O2­binding protein found in the muscles of marine invertebrates. Hr and Mr possess one binuclear iron centre (per subunit), and are often described according to oxidation and ligation states of the iron centre:

O2 binding is essentially noncooperative for Hr. The uptake of O2 by Hr is accompanied by two­electron oxidation of the reduced binuclear centre to produce bound peroxide (OOH-). The chemistry of O2 binding by Hr is summarised in Scheme (1) [2]. Deoxy­Hr contains two high­spin ferrous ions bridged by hydroxyl ion (I). The bridging hydroxyl serves as the proton donor for peroxide after O2 binding, resulting in the formation of a µ­oxo bridge in oxy­ and met­Hr. O2 binds to the pentacoordinate FeII at the vacant coordination site (II). Then electrons are transferred from the ferrous ions to generate the binuclear ferric centre with bound OOH- (III).

3­D structures of Hr and Mr are known [3, 4]. The iron ions are coordinated in a four­alpha­helix bundle by five His residues and bridged by two carboxylate residues and a hydroxyl or an oxo group (see Figure 1HMO).

Haemerythrin family in motif databases

PRINTS ID PRINTS AC PROSITE/BLOCKS ID PROSITE AC BLOCKS AC
HEMERYTHRIN PR00186 HEMERYTHRINS PS00550 BL00550

Haemerythrin­like proteins in alignment databases

Protein Superfamily Pfam LPFC 3­D
alignment
01293; hemerythrin
-
-

Haemerythrin­like proteins in 3­D databases

Haemerythrin­like proteins contain a single binuclear iron centre (see Figure 1HMO).

PDB scop BSMRELI
Base		 Header
1a7d
-
 1a7d
-
 Myohaemerythrin (chloro­met); Themiste zostericola (sipunculid worm)
1a7e
-
 1a7e
-
 Myohaemerythrin (hydroxo­met) (complex with Cl¯); Themiste zostericola (sipunculid worm)
1hmd 1hmd 1hmd 1hmd Haemerythrin (deoxy) (complex with acetate); Themiste dyscrita (sipunculid worm)
1hmo 1hmo 1hmo 1hmo Haemerythrin (oxy) (complex with acetate); Themiste dyscrita (sipunculid worm)
1hr3 1hr3 1hr3 1hr3 Haemerythrin (azido­met) (Calpha atoms only); Siphonosoma sp.
1hrb 1hrb 1hrb 1hrb Haemerythrin (Calpha atoms only); Phascolopsis gouldii (syn. Golfingia gouldii, marine worm)
2hmq 2hmq 2hmq 2hmq Haemerythrin (met) (complex with acetate); Themiste dyscrita (sipunculid worm)
2hmz 2hmz 2hmz 2hmz Haemerythrin (azido­met) (complex with acetate); Themiste dyscrita (sipunculid worm)
2mhr 2mhr 2mhr 2mhr Myohaemerythrin (azido­met) (complex with sulphate); Themiste zostericola (sipunculid worm)

References

  1. Nordlund, P. and Eklund, H. (1995) Di­iron-carboxylate proteins. Curr. Opin. Struct. Biol. 5, 758-766.
  2. Cowan, J.A. (1993) Inorganic Biochemistry: An Introduction. VCH Publishers, New York.
  3. Holmes, M.A., Le Trong, I., Turley, S., Sieker, L.C. and Stenkamp, R.E. (1991) Structures of deoxy and oxy hemerythrin at 2.0 Å resolution. J. Mol. Biol. 218, 583-593.
  4. Sheriff, S., Hendrickson, W.A. and Smith, J.L. (1987) Structure of myohemerythrin in the azidomet state at 1.7/1.3 Å resolution. J. Mol. Biol. 197, 273-296.
Bibliography on structural studies of haemerythrin family proteins
Reviews on haemerythrin family proteins