Myoglobin

Abstract

Myoglobin is a small globular monomeric protein, expressed in the red muscles of vertebrates, where it serves as molecular oxygen storage and delivery and as nitric oxide scavenger.

It can reversibly bind oxygen thanks to the presence of a prosthetic group, the haem, which is hosted in a fairly hydrophobic crevice, within the protein matrix. The iron is responsible of keeping the haem inside the protein being coordinated to the so‐called proximal histidine. On the sixth coordination site, Fe(II) is able to combine with high affinity, but reversibly, with O2 and several other ligands.

The iron–ligand bond is broken by light; therefore, Mb has also been employed for exploring the very first relaxation events after photodissociation by fast and ultra‐fast kinetic methods.

Mb has also been a molecule of choice in unveiling the role of molecular motions in controlling function and stability of proteins.

Key Concepts

  • Myoglobin (Mb) is a water‐soluble globular protein of molecular weight 17 000 Da, expressed in the skeletal muscles and the heart.
  • The α‐helical organisation of the polypeptide chain yields a unique topology called the ‘globin fold’.
  • Its red colour is due to one molecule of Fe(II) haem, bound in a crevice of the globin in between helices E and F.
  • Mb's function is intracellular oxygen transport/storage, and nitric oxide scavenging.
  • Mb has been the paradigm for the discovery and the studies of protein plasticity and dynamics.
  • The photolability of the iron–ligand bond has been exploited for laser‐activated transient relaxation.
  • Many of the advanced biophysical techniques now available have been developed and tested on Mb.
  • Mb has been a benchmark for bioinformatics topological annotation and molecular dynamics simulations.
  • Globins paved the way to the concepts of molecular clock and molecular evolution, as they are expressed in all phyla.
  • Early studies on the structure–function relationships in Mb have represented a proof‐of‐principle of this powerful approach.

Keywords: globin fold; haem; oxygen storage; functional and structural dynamics; evolution

Figure 1. The structure of myoglobin. (a) Ball‐and‐stick representation of the haem bound to the active site of sperm whale oxymyoglobin (Protein Data Bank id: 1MBO). Key residues on the distal and proximal haem pocket are also shown, labelled following the topological annotation. Note the hydrogen bond between the Nϵ of the distal His E7 and the oxygen molecule, which is bound at an angle of about 130°. Neutron diffraction, NMR and computational chemistry have shown that in MbO2 this amino acid is protonated only on Nϵ. It may be noticed that in the CO derivative protonation also occurs on Nδ, which faces the bulk water, thereby favouring a more perpendicular geometry. (b) Ribbon representation of sperm whale myoglobin, highlighting the 3/3 globin fold. Side chains have been omitted for clarity. Helices are indicated with capital letters (A through H) from the N‐terminus to the C‐terminus. The haem group is in gold stick representation.
Figure 2. Oxygen reactivity curves of haemoglobin (Hb), Mb and cytochrome oxidase (COX) expressed as percentage of protein oxygenation at pH 7.4 as a function of oxygen concentration in mol/L (M). It may be noticed that the gradient of oxygen affinities of the three proteins correlates with the increasing local concentration of the gas in going from mitochondria to blood (RBC).
Figure 3. Ligand migration pathway within the protein matrix. The combination of structural dynamics, mainly by picosecond laser photolysis coupled with Laue crystallography, and static structure determination in the presence of 30 atm of Xenon demonstrated the importance of the small solvent excluded internal cavities in the modulation of ligand binding. The structure of the main chain is represented in ribbon coloured from red to blue starting from the N‐terminus. The haem, His F8 and His E7 are in stick representation with the atoms coloured by their canonical code (C green, O red, N blue, Fe grey). CO is in van der Waals representation; the cavities occupied by Xe atoms (PDB: 4NXA) are in light grey. (a) The structure of Mb–CO (PDB: 1MYZ); notice the CO bound to the haem iron which is flat. (b) The first photolytic intermediate trapped at cryogenic temperature (20 K in liquid helium). The photolyzed CO, which lies in the distal pocket parallel to the haem (PDB: 1DXD), may either rebind directly to the haem iron in a reaction called geminate recombination, or migrate in the protein matrix populating the Xe binding cavities. (c) The CO is momentarily trapped in the so‐called Xe4 cavity (PDB: 1DWS). Subsequently, the CO is observed inside the proximal Xe1 cavity (PDB: 1DWT) as shown in (d). The dynamics of these events, which range from femtoseconds to 100 nanoseconds, is best illustrated in the movie available as Supplementary video 1. We express our appreciation to A. Di Nola (‘Sapienza’ University of Rome) and A. Amadei (University of Rome ‘Tor Vergata’) for the MD calculations and to G. Giardina (‘Sapienza’ University of Rome) for the final wrap‐up of the movie.
Figure 4. The evolution of vertebrate globins. A phylogenetic tree has been built based on amino acid sequence similarities between the globins belonging to the superfamily. The y‐axis indicates the time in millions of years, from today backwards to about 1 billion years. Branching from a common ancestor has first seen the divergence of neuroglobin from cellular globins. Neuroglobin is found in the brain and has a role in the protection from injuries due to reactive oxygen and nitrogen species. The second branch saw the separation of monomeric from polymeric globins. About 500 millions years ago, cytoglobin (found in the liver) and Mb (in the muscles) diverged. Subsequently, the separation between the α and β chains of haemoglobin has been mapped about 400 million years ago. In primates, neuroglobin, cytoglobin, Mb and the clusters of the α and the β chains of haemoglobin are on five different chromosomes (as boxed on the top of the figure).
close

References

Ansari A, Jones CM, Henry ER, Hofrichter J and Eaton WA (1992) The role of solvent viscosity in the dynamics of protein conformational changes. Science 256 (5065): 1796–1798.

Antonini E and Brunori M (1971) Hemoglobin and Myoglobin in their Reactions with Ligands. Amsterdam: North‐Holland Publishing Company.

Austin RH, Beeson KW, Eisenstein L, Frauenfelder H and Gunsalus IC (1975) Dynamics of ligand binding to myoglobin. Biochemistry 14: 5355–5373.

Bossa C, Amadei A, Daidone I, et al. (2005) Molecular dynamics simulation of sperm whale myoglobin: effects of mutations and trapped CO on the structure and dynamics of cavities. Biophysical Journal 89 (1): 465–474.

Bourgeois D, Vallone B, Schotte F, et al. (2003) Complex landscape of protein structural dynamics unveiled by nanosecond Laue crystallography. Proceedings of the National Academy of Science USA 100 (15): 8704–8709.

Brunori M (2010) Myoglobin strikes back. Protein Science 19: 195–201.

Brunori M, Vallone B, Cutruzzola F, et al. (2000) The role of cavities in protein dynamics: crystal structure of a photolytic intermediate of a mutant myoglobin. Proceedings of the National Academy of Sciences USA 97 (5): 2058–2063.

Burmester T, Weich B, Reinhardt S and Hankeln T (2000) A vertebrate globin expressed in the brain. Nature 407 (6803): 520–523.

Dezfulian C, Alekseyenko A, Dave KR, et al. (2012) Nitrite therapy is neuroprotective and safe in cardiac arrest survivors. Nitric Oxide 26: 241–250.

Dickerson RE and Geis I (1983) Hemoglobin. Menlo Park, CA: Benjamin/Cummings.

Eich RF, Li T, Lemon DD, et al. (1996) Mechanism of NO‐induced oxidation of myoglobin and hemoglobin. Biochemistry 35: 6976–6983.

Elber R and Karplus M (1987) Multiple conformational states of proteins: a molecular dynamics analysis of myoglobin. Science 235 (4786): 318–321.

Elber R and Gibson QH (2008) Toward quantitative simulations of carbon monoxide escape pathways in myoglobin. Journal of Physical Chemistry B 112 (19): 6147–6154.

Fitch WM and Langley CH (1976) Protein evolution and the molecular clock. Federation Proceedings 35 (10): 2092–2097.

Flögel U, Merx MW, Godecke A, Decking UK and Schrader J (2001) Myoglobin: a scavenger of bioactive NO. Proceedings of the National Academy of Sciences USA 98: 735–740.

Frauenfelder H, McMahon BH and Fenimore PW (2003) Myoglobin: the hydrogen atom of biology and a paradigm of complexity. Proceedings of the National Academy of Sciences USA 100 (15): 8615–8617.

Frauenfelder H, Petsko GA and Tsernoglou D (1979) Temperature‐dependent X‐ray diffraction as a probe of protein structural dynamics. Nature 280 (5723): 558–563.

Fridovich I (1962) Competitive inhibition by myoglobin of the reduction of cytochrome c by xanthine oxidase. The Journal of Biological Chemistry 237: 584–586.

Friedman JM and Lyons KB (1980) Transient Raman study of CO‐haemoprotein photolysis: origin of the quantum yield. Nature 284: 570–572.

Garry DJ, Ordway GA, Lorenz JN, et al. (1998) Mice without myoglobin. Nature 395: 905–908.

Gibson QH (1989) Hemoproteins, ligands, quanta. The Journal of Biological Chemistry 264: 20155–20158.

Gödecke A, Flögel U, Zanger K, et al. (1999) Disruption of myoglobin in mice induces multiple compensatory mechanisms. Proceedings of the National Academy of Sciences USA 96: 10495–10500.

Günther H (1921) Über den Muskelfarbstoff. Virchows Archives 230: 146–178.

Hendgen‐Cotta UB, Merx MW, Shiva S, et al. (2008) Nitrite reductase activity of myoglobin regulates respiration and cellular viability in myocardial ischemia‐reperfusion injury. Proceedings of the National Academy of Sciences USA 105: 10256–10261.

Henry ER, Sommer JH, Hofrichter J and Eaton WA (1983) Geminate recombination of carbon monoxide to myoglobin. Journal of Molecular Biology 166: 443–451.

Hoard JL (1971) Stereochemistry of hemes and other metalloporphyrins. Science 174: 1295–12302.

Kadish KM, Smith KM and Guilard R (2000) The Porphyrin Handbook. London, UK: Academic Press.

Kendrew JC, Bodo G, Dintzis HM, et al. (1958) A three‐dimensional model of the myoglobin molecule obtained by x‐ray analysis. Nature 181: 662–666.

Kendrew JC (1963) Myoglobin and the structure of proteins. Science 139: 1259–1266.

Kimura M (1986) DNA and the neutral theory. Philosophical Transactions of the Royal Society, London B Biological Sciences 312: 343–354.

Lee B and Richards FM (1971) The interpretation of protein structures: estimation of static accessibility. Journal of Molecular Biology 55: 379–400.

Moffat K, Szebenyi D and Bilderback D (1984) X‐ray Laue diffraction from protein crystals. Science 223: 1423–1425.

Olson JS and Phillips GN Jr (1996) Kinetic pathways and barriers for ligand binding to myoglobin. The Journal of Biological Chemistry 271: 17593–17596.

Pauling L and Coryell CD (1936) The magnetic properties and structure of hemoglobin, oxyhemoglobin and carbonmonoxyhemoglobin. Proceedings of the National Academy of Sciences USA 22: 210–216.

Perutz MF (1983) Species adaptation in a protein molecule. Molecular Biology and Evolution 1: 1–28.

Pesce A, Bolognesi M, Bocedi A, et al. (2002) Neuroglobin and cytoglobin. Fresh blood for the vertebrate globin family. EMBO Reports 3: 1146–1151.

Phillips SE and Schoenborn BP (1981) Neutron diffraction reveals oxygen‐histidine hydrogen bond in oxymyoglobin. Nature 292: 81–82.

Ptitsyn OB (1995) Molten globule and protein folding. Advances in Protein Chemistry 47: 83–229.

Reeder BJ, Svistunenko DA, Cooper CE and Wilson MT (2004) The radical and redox chemistry of myoglobin and hemoglobin: from in vitro studies to human pathology. Antioxidant and Redox Signalling 6: 954–966.

Schlichting I and Chu K (2000) Trapping intermediates in the crystal: ligand binding to myoglobin. Current Opinion in Structural Biology 10: 744–752.

Schotte F, Lim M, Jackson TA, et al. (2003) Watching a protein as it functions with 150‐ps time‐resolved x‐ray crystallography. Science 300: 1944–1947.

Scott EE, Gibson QH and Olson JS (2001) Mapping the pathways for O2 entry into and exit from myoglobin. The Journal of Biological Chemistry 276: 5177–5188.

Shulman RG, Wüthrich K, Yamane T, Antonini E and Brunori M (1969) Nuclear magnetic resonances of reconstituted myoglobins. Proceedings of the National Academy of Sciences USA 63: 623–628.

Spiro TG (1985) Resonance Raman spectroscopy as a probe of heme protein structure and dynamics. Advances in Protein Chemistry 37: 111–159.

Tilton RF Jr, Kuntz ID Jr and Petsko GA (1984) Cavities in proteins: structure of a metmyoglobin‐xenon complex solved to 1.9 Å. Biochemistry 23: 2849–2857.

Vinogradov SN, Hoogewijs D, Bailly X, et al. (2005) Three globin lineages belonging to two structural classes in genomes from the three kingdoms of life. Proceedings of the National Academy of Sciences USA 102: 11385–11389.

Wittenberg JB (1970) Myoglobin facilitated oxygen diffusion and the role of myoglobin in oxygen entry into muscle. Physiology Reviews 50: 559–636.

Wittenberg BA and Wittenberg JB (1989) Transport of oxygen in muscle. Annual Review of Physiology 51: 857–878.

Wyman J (1966) Facilitated diffusion and the possible role of myoglobin as a transport mechanism. The Journal of Biological Chemistry 241: 115–121.

Yonetani T, Yamamoto H and Iizuka T (1974) Studies on cobalt myoglobins and hemoglobins. 3. Electron paramagnetic resonance studies of reversible oxygenation of cobalt myoglobins and hemoglobins. The Journal of Biological Chemistry 249: 2168–2174.

Further Reading

Brunori M (2001) Nitric oxide moves myoglobin centre stage. Trends in Biochemical Sciences 26: 209–210.

Burmester T and Hankeln T (2014) Function and evolution of vertebrate globins. Acta Physiologica (Oxford) 211: 501–514.

Chance B, Fischetti R and Powers L (1983) Structure and kinetics of the photoproduct of carboxymyoglobin at low temperatures: an X‐ray absorption study. Biochemistry 22: 3820–3829.

Dayhoff MO (1965) The Atlas of Protein Sequence and Structure. National Biomedical Research Foundation, Silver Spring, Maryland, USA. (doi per link 10.1002/9780470015902.a0023939).

Flögel U, Gödecke A, Klotz LO and Schrader J (2004) Role of myoglobin in the antioxidant defence of the heart. The FASEB Journal 18: 1156–1158.

Kitagawa T, Kyogoku Y, Iizuka T and Saito MI (1976) Nature of the iron‐ligand bond in ferrous low spin hemoproteins studied by resonance Raman scattering. Journal of the American Chemical Society 98: 5169–5173.

Livingston DJ, LaMar GN and Brown WD (1983) Myoglobin diffusion in bovine heart muscle. Science 220: 71–73.

Powers L, Chance B, Chance M, et al. (1987) Kinetic, structural, and spectroscopic identification of geminate states of myoglobin: a ligand binding site on the reaction pathway. Biochemistry 26: 4785–4796.

Rossmann MG (1994) The beginnings of structural biology. Recollections, special section in honor of Max Perutz. Protein Science 3: 1731–1733.

Srajer V, Teng T, Ursby T, et al. (1996) Photolysis of the carbon monoxide complex of myoglobin: nanosecond time‐resolved crystallography. Science 274: 1726–1729.

Contact Editor close
Submit a note to the editor about this article by filling in the form below.

* Required Field

How to Cite close
Brunori, Maurizio, and Miele, Adriana E(Aug 2015) Myoglobin. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0000656.pub2]