Myohemerythrin structure

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.

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. 

Takagi, T. and Cox, J. A. (1991). Primary structure of myohemerythrin from the annelid Nereis diversicolor. EEBS Letters, 285, 25-7. 

Figure 1. Schematic representations of protein structures (a) myohemerythrin, an a-helical protein with antiparallel helices ( >) V2 domain of an immunoglobulin, a (3-sheet protein (c) triose phosphate isomerase, a parallel a-ff protein with a central (3 barrel (d) carboxypepti-dase, a parallel a- 3 protein with a central ( -sheet structure (e)para-hydroxybenzoate hydrolase, a complex protein structure with more than one domain. (From Ref. S3 courtesy of J. Richardson.)...

J. Kuriyan, A. T. Briinger, M. Karplus, and W. A. Hendrickson, Acta Crystallogr., Sect. A, 45, 396 (1989). X-Ray Refinement of Protein Structures by Simulated Annealing Test of the Method on Myohemerythrin. 

Figure V-g shows the primary structure of Hr obtained from G. gouldii, while Fig. V-9 shows the tertiary structure of monomeric myohemerythrin obtained by low-resolution X-ray analysis it consists of four nearly parallel helical segments. 30-40 A long, connected by sharp nonhelical turns.

D. Rojewska and R. Elber, Proteins Struct. Funct. Genet., 7, 265 (1990). Molecular E -namics Study of Secondary Structure Motions in Proteins Application to Myohemerythrin. 

At least some hemerythrin-containing animals also have a monomeric hemerythrin present in their muscles. This protein, myohemerythrin, is homologous with the subunits of octameric hemerythrin (Hendrickson and Ward, 1977 Ward and Hendrickson, 1977), though its primary structure is substantially different from coelomic hemerythrins (Klippenstein et al, 1976). 

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