Myohemerythrin

Figure 18.11 Electron-density maps at different resolution show more detail at higher resolution, (a) At low resolution (5.0 A) individual groups of atoms are not resolved, and only the rodlike feature of an

Although semi-met forms of myohemerythrin (the monomeric protein from Themiste zostericola muscle) can be obtained in a similar manner to the octamer (32), the intramolecular disproportionation path is obviously now unavailable to them. In... 

Fig. 19. Examples of the two commonest types of helix-helix contact (a) Class II (from hexokinase) with an interhelix angle of about -60° (b) Class III (from myohemerythrin) with an interhelix angle of about +20°.

A. Up-and-down helix bundles Myohemerythrin, hemerythrin Cytochrome b5(B Cytochrome c ... 

HA1 jellyroll Greek key /3 barrel HA2 open-face /3 sandwich HA2 around 3-fold miscellaneous helix cluster Hemerythrin (Stenkamp et al., 1978), see Myohemerythrin Hemoglobin (Ladner et al., 1977)... 

Myoglobin (Watson, 1969), see Hemoglobin Myohemerythrin (Hendrickson and Ward, 1977)... 

Fig. 87. Myohemerythrin as an example of an up-and-down helix bundle, (a) a-Carbon stereo (b) schematic drawing of the backbone structure, from the same viewpoint as in a.

Pancreatic ribonuclease Staphylococcal nuclease Peroxidases Glutathione peroxidase Cytochrome c peroxidase Oxygen carriers Myoglobin, hemoglobin Myohemerythrin, hemerythrin Hormone-binding proteins Uteroglobin Pre albumin Lectins... 

The best characterized and thus prototypical of the binuclear iron-oxo proteins is hemerythrin (Hr), an oxygen carrier from some classes of marine invertebrates, such as sipunculids. The protein consists of several identical 13 kDa subunits which contain two iron atoms and reversibly bind one molecule of O2. Myohemerythrins contain a single 13 kDa subunit (25,26,27). 

The structure of the ternap bioinorganie complex metazido myohemerythrin, from sipunculan worms, is outlined in (53)." ... 

A representative sampling of non-heme iron proteins is presented in Fig. 3. Evident from this atlas is the diversity of structural folds exhibited by non-heme iron proteins it may be safely concluded that there is no unique structural motif associated with non-heme iron proteins in general, or even for specific types of non-heme iron centers. Protein folds may be generally classified into several categories (i.e., all a, parallel a/)3, or antiparallel /8) on the basis of the types and interactions of secondary structures (a helix and sheet) present (Richardson, 1981). Non-heme iron proteins are found in all three classes (all a myohemerythrin, ribonucleotide reductase, and photosynthetic reaction center parallel a/)8 iron superoxide dismutase, lactoferrin, and aconitase antiparallel )3 protocatechuate dioxygenase, rubredoxins, and ferredoxins). This structural diversity is another reflection of the wide variety of functional roles exhibited by non-heme iron centers. 

Fig. 11. Environment of the binuclear irons in myohemerythrin. (Reproduced with permission from Sheriff etal., 1987.)...

Myohemerythrin, 43 363 MjYj uansition metal halide clusters, see Group 6 metal halide clusters M Yjj transition metal halide clusters, see Group 5 metal halide clusters... 

Figure 2-22 Ribbon drawing of an up-and-down four-helix bundle in myohemerythrin. The two spheres represent the two iron atoms which carry an 02 molecule. They are coordinated by histidine and aspartate side chains. Courtesy of J. Richardson.117...

Abbreviations MBN, myoglobin MGN, myogen MHN, myohemerythrin RUB, mbredoxin ICG, immunoglobulin constant region IGV, immunoglobulin variable region PBN, prealbumin SDM, superoxide dismutase CON, conconavalin A CHT, chymotrypsin INS, insulin PTI, pancreatic trypsin inhibitor CB5, cytochrome b5 ... 

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