Myoglobin globin fold

Figure 3.13 The hemoglobin molecule is built up of four polypeptide chains two a chains and two (3 chains. Compare this with Figure 1.1 and note that for purposes of clarity parts of the a chains are not shown here. Each chain has a three-dimensional structure similar to that of myoglobin the globin fold. In sicklecell hemoglobin Glu 6 in the (3 chain is mutated to Val, thereby creating a hydrophobic patch on the surface of the molecule. The structure of hemoglobin was determined in 1968 to 2.8 A resolution in the laboratory of Max Perutz at the MRC Laboratory of Molecular Biology, Cambridge, UK.

Figure 4.11 (a) Four helix bundle domain proteins, illustrated by myohaemerythrin. The oxygenbinding site is located at the di-iron centre within the hydrophobic core of the helical bundle, (b) The globin fold, represented here by myoglobin. (From Branden and Tooze, 1991. Reproduced by permission of Garland Publishing, Inc.)... 

Answer Myoglobin is all three. The folded structure, the globin fold, is a motif found in all globins. The polypeptide folds into a single domain, which for this protein represents the entire three-dimensional structure. 

Another important helical domain is the globin fold, found in the first protein for which the three-dimensional structure was determined, the oxygen storage protein, myoglobin (Figure 3.15b), from the muscle of the sperm... 

Globin fold The three-dimensional structure of the proteins that is common to myoglobin and the subunits of hemoglobin. 

The tertiary structure of myoglobin consists of eight a-helices connected by short coils, a structure that is known as the globin fold (see Fig. 7.11). This structure is unusual for a globular protein in that it has no (3-sheets. The helices create a hydrophobic O2 binding pocket containing tightly bonnd heme with an iron atom (Fe ) in its center. 

Although the amino acid sequences of myoglobin and hemoglobin are homologous, and they adopt the same globin fold, there are important differences in patches where the polypeptide chains in hemoglobin make contact with one... 

The main chain of myoglobin, illustrating the "globin fold," typic of all globins. 

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