Myoglobin globin fold


The first globular protein structure that was determined, myoglobin, belongs to the class of alpha- (a-) domain structures. The structure illustrated in Figure 2.9 is called the globin fold and is a representative example of one class of a domains in proteins short a helices, the building blocks, are connected by loop regions and packed together to produce a hydrophobic core. Packing interactions within the core hold the helices together in a stable globular structure, while the hydrophilic residues on the surface make the protein soluble in water. In this chapter we will describe some of the different a-domain structures in soluble proteins.  [c.35]

The globin fold is present in myoglobin and hemoglobin  [c.40]

The pairwise arrangements of the sequential a helices in the globin fold are quite different from the antiparallel organization found in the four-helix-bundle a structures. The globin structure is a bundle of eight a helices, usually labeled A-H, connected by rather short loop regions and arranged so that the helices form a pocket for the active site, which in myoglobin and the hemoglobins binds a heme group (Figure 3.10). The lengths of the a helices vary considerably, from 7 residues in the shortest helix (C) to 28 in the longest helix (H) in myoglobin. In the globin fold the a helices wrap around the core in different directions so that sequentially adjacent a helices are usually not adjacent to each other in the structure. The only exceptions are the last two a helices (G and H), which form an antiparallel pair with extensive packing interactions between them. All other packing interactions are formed between pairs of a helices that are not sequentially adjacent. Because the globin fold is not built up from an assembly of smaller motifs, it is quite difficult to visualize conceptually in spite of its relatively small size and simplicity.  [c.40]

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 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.
One of the most important a structures is the globin fold. This fold has been found in a large group of related proteins, including myoglobin, hemoglobins, and the light-capturing assemblies in algae, the phycocyanins. The functional and evolutionary aspects of these structures will not be discussed in this book instead, we will examine some features that are of general structural interest.  [c.40]


Introduction to protein structure (1999) -- [ c.40 ]