Myohemerythrin


The four-helix bundle occurs in several widely different proteins, such as myohemerythrin (an oxygen-transport protein in marine worms that does not contain heme iron), cytochrome c and cytochrome bs62 (heme-containing electron carriers) (Figure 3.7a), ferritin (a storage molecule for iron atoms in eucaryotic cells), and the coat protein of tobacco mosaic virus. In these examples, sequentially adjacent a helices ate always antiparallel. However, four-helix bundles can also be formed with different topological arrangements of the a helices. In human growth hormone (Figure 3.7b), a four-helix bundle is formed from two pairs of parallel a helices that are joined in an  [c.37]

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 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 <x helix can be deduced, (b) At medium resolution (3.0 A) the path of the polypeptide chain can be traced, and (c) at high resolution (1.5 A) individual atoms start to become resolved. Relevant parts of the protein chain (red) are superimposed on the electron densities (gray) The diagrams show one <x helix from a small protein, myohemerythrin. [Adapted from W.A. Hendrickson in Protein Engineering (eds. D.L. Oxender and C.F. Fox.), p. 11.

See pages that mention the term Myohemerythrin : [c.46]   
Introduction to protein structure (1999) -- [ c.37 , c.381 ]