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| [[Image:1a6m.png|left|200px|thumb|Crystal Structure of myoglobin, [[1a6m]]]]
| | <StructureSection load='1a6m' size='350' side='right' caption='Structure of Sperm whale myoglobin containing protoporphyrin with O2 and sulfate (PDB entry [[1a6m]])' scene=''> |
| {{STRUCTURE_1a6m| PDB=1a6m | SIZE=400| SCENE='Myoglobin/Myoglobin/2 right'|CAPTION=Sperm whale myoglobin complex with O2 and sulfate, [[1a6m]] }}
| | __TOC__ |
| | == Function == |
| | [[Myoglobin]] is a protein found in muscle tissues that plays a critical role in the storage and transport of oxygen. It is structurally and functionally related to hemoglobin, the protein responsible for oxygen transport in red blood cells. While hemoglobin carries oxygen throughout the body, myoglobin is primarily found in muscle cells and facilitates the uptake and release of oxygen within the muscles themselves. |
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| | == Structural highlights == |
| | Myoglobin is a globular protein whose function is to store molecular oxygen in muscles (myo = muscles)<ref>PMID:15339940</ref>. It has two main components: a single polypeptide chain, and heme ligand. The heme ligand is only <scene name='23/238129/Transparent_spacefill/2'>partially exposed</scene> to the surface; the majority of it is buried inside the protein. The overall <scene name='23/238129/Surface/1'>shape</scene> of myoglobin is approximately disc-shaped with a diameter that is about twice its thickness. The overall fold of the protein is conserved, especially the <scene name='23/238129/Hydrophobic/1'>hydrophobic</scene> core of the protein (shown in purple), but the sequence is more <scene name='23/238129/Conserved_cartoon/1'>variable</scene> on the surface. {{Template:ColorKey_ConSurf_NoYellow_NoGray}} '''Metmyoglobin''' (MMb) is the oxidized form of myoglobin.The globin consists mostly of [[Helices in Proteins|alpha helices]] shown in <scene name='23/238129/2ndary_structure/2'>pink</scene>; it has no beta sheets and its non-helical segments mostly serve as links that connect the helices. Look down the barrel of some of the longer helices. Are they all straight? The eight structurally conserved alpha helices are labelled <scene name='23/238129/Helix_labels/2'>A through H</scene>. The protein is colored as a N-->C rainbow in this view; the N terminus is blue, while the C terminus is red. |
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| | The <scene name='23/238129/Heme/2'>heme ligand</scene>, and specifically the iron atom in the middle of the heme, is what binds oxygen in myoglobin. In this representation, the heme alone is shown in ball and stick form with its C, N and O atoms displayed as grey, blue, and red balls respectively. The iron atom is shown in orange, and is in spacefilling mode to better illustrate its interactions with the heme. The iron is bound by four nitrogen atoms found in the heme ring, as well as an <scene name='23/238129/Fe_ligands/1'>amino acid</scene> from the protein chain. Which amino acid from the myoglobin protein binds to the iron? Notice that in the oxygenated state, the iron is in the plane of the heme ring. In the <scene name='23/238129/Deoxy_heme_fe_plane/1'>deoxy</scene> (no oxygen) state, the Fe atom is slightly above the plane of the heme, and a second <scene name='23/238129/Deoxy_heme_his/1'>amino acid</scene> coordinates with the iron in the heme ring. |
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| | == Function == |
| | The main function of myoglobin is to store oxygen in muscle tissues and provide a readily available supply during periods of increased demand, such as during muscle contraction or exercise. When the muscle cells have an ample supply of oxygen, myoglobin binds to oxygen molecules, effectively storing them within the muscle fibers. |
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| | During periods of oxygen deficiency, such as during intense exercise when oxygen demand exceeds supply, myoglobin releases the stored oxygen to the surrounding muscle cells. This ensures that the muscle cells have a sufficient oxygen supply to support their metabolic needs, facilitating aerobic respiration and energy production. |
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| | The affinity of myoglobin for oxygen is higher than that of hemoglobin, which allows myoglobin to extract oxygen from hemoglobin in the bloodstream when oxygen levels are low. This property enables efficient oxygen transfer from the bloodstream to the muscle tissues. |
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| | The red color of muscle tissues is attributed to the presence of myoglobin, as it binds oxygen, giving the oxygenated muscle a characteristic reddish appearance. |
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| | Myoglobin is also used as a diagnostic marker for certain medical conditions. For example, elevated levels of myoglobin in the blood can indicate muscle damage or injury, such as in cases of heart attacks or skeletal muscle trauma. |
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| | In summary, myoglobin is a protein found in muscle tissues that functions as an oxygen reservoir, allowing the efficient storage and release of oxygen within muscle cells. Its ability to bind and release oxygen helps sustain aerobic respiration in muscles during times of increased demand, such as during exercise. |
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| | == Additional details == |
| | [[Oxymyoglobin]] for myoglobin complex with O2 <br /> |
| | [[Porphyrin]] for porphyrin.<br /> |
| | [[Molecular Playground/Myoglobin]]<br /> |
| | [[Myoglobin of Physeter catodon: structure]]<br /> |
| | [[Extremophile]]<br /> |
| | [[Extremophiles]] |
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| | | [[Myoglobin-Physeter-catodon-structure]] (Spanish)<br /> |
| | | [[Myoglobin (Hebrew)]]<br /> |
| | | [[Myoglobin (arabic)]]. |
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| [[Myoglobin]] is a globular protein whose function is to store molecular oxygen. | |
| <kinemage align="right" width="650" height="500" file="Myoglobin.kin" /> | |
| View1 shows a ribbon diagram, in gray, of the "Globin" (protein) portion of sperm whale deoxymyoglobin in which its eight helical segments, A through H, are displayed with two strands. Use the "zoom" slider to properly size the molecule in the viewer. Toggle the "ANIMATE" button to sequentially color these helices and their preceding nonhelical segments in rainbow order. You can see that the globin consists mostly of [[Helices in Proteins|alpha helices]]; it has no beta sheets and its nonhelical segments mostly serve as links that connect the helices. Look down the barrel of some of the longer helices. Are they all straight?
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| The heme is shown, in pink, in wireframe form with its N, O, and Fe atoms displayed as blue, red, and orange balls. Note how the heme is almost completely enclosed by the globin. Which few chemical groups of the Heme are exposed to the solvent? (Clicking on atoms displays their identity in the lower left hand corner.) Can you rationalize this exposure?
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| View1 is the standard view of Mb. Rotate the protein around to convince yourself that the globin is approximately disc-shaped with a diameter that is about twice its thickness. Turn on the "Main Chain" button to display the polypeptide backbone in white with its N and O atoms represented by blue and red balls. How closely does the ribbon follow the main chain?
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| Click "Animate" until the Mb ribbon is gray. Turn off the "Mb Ribbon" button. What are the orientations of the main chain carbonyl groups and the amide N atoms relative to each other which allows formation of the H-bonds of the alpha helices (not drawn)?
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| View2 is a closeup of the heme from the same direction as View1. Turn on the "HemeLigand" button to display, in cyan, the sidechain of His 93, the proximal His, liganding the heme's Fe(II) ion (white bond). The Fe(II) is also liganded in a square-planar array by the heme's four pyrrole N atoms and hence has a total of 5 pyramidally arranged ligands. In oxyMb, the reversibly bound O2 molecule ligands the Fe from the opposite side of the heme as does the proximal His so that the Fe(II) becomes octahedrally coordinated. The Fe atom is not oxidized by its O2 ligand; it remains in the Fe(II) oxidation state.
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| Rotate the image about the vertical axis until you see heme edge-on. Is the Heme planar? Note that the Fe atom is displaced towards the proximal His by 0.55 Å from the best plane though the porphyrin ring atoms. In oxyMb, the Fe is only 0.22 Å out of the heme plane and still on the side of the proximal His (for details see [[Oxymyoglobin]]). See also [[Molecular Playground/Myoglobin]].
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| Exercise in large part by John H. Connor (present address: Department of Microbiology, Boston University School of Medicine, 850 Harrison Ave, Boston, MA, 02118, USA)
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| {{TOC limit|limit=2}}
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| == 3D Structures of Myoglobin == | | == 3D Structures of Myoglobin == |
| | [[Myoglobin 3D structures]] |
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| ''Update June 2012''
| | </StructureSection> |
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| Myoglobin (Mb) is an oxygen binding protein found in muscle tissue. It contains a heme group. Metmyoglobin (MMb) is the oxidized form of myoglobin.
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| === Mb wild type ===
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| [[2zsn]], [[2zso]], [[2zsp]], [[2zsq]], [[2zsr]], [[2zss]], [[2zst]], [[2zsx]], [[2zsy]], [[2zsz]], [[2zt0]], [[2zt1]], [[2zt2]], [[2zt3]], [[2zt4]], [[3e4n]], [[3e55]], [[3e5i]], [[3e5o]], [[3ecl]], [[3ecx]], [[3ecz]], [[3ed9]], [[3eda]], [[3edb]], [[2z6s]], [[1u7r]], [[1u7s]], [[1jp6]], [[1jp8]], [[1jp9]], [[1jpb]], [[1jw8]], [[1f6h]], [[1bz6]], [[1bzp]], [[1a6k]], [[1a6n]], [[1vxa]], [[1vxb]], [[1vxc]], [[1vxd]], [[1vxe]], [[1vxf]], [[1vxg]], [[1vxh]], [[1mlq]], [[1moa]], [[1mob]], [[1moc]], [[1mod]], [[4mbn]], [[5mbn]], [[1mbn]] – SwMb - Sperm whale<br />
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| [[1l2k]], [[1cq2]], [[1mbd]] – SwMb – Neutron<br />
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| [[1wla]], [[1hsy]], [[2v1e]], [[2v1f]], [[2v1g]], [[2v1h]], [[2v1i]], [[2v1j]], [[2v1k]] – hoMb - horse<br />
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| [[2nrl]] – BtMb – Blackfin tuna<br />
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| [[1mba]], [[3mba]], [[4mba]] – AlMb - ''Aplysia limacine''<br />
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| [[1m6m]], [[1mwd]], [[1mnh]], [[1mnj]], [[1mnk]], [[1ycb]], [[1pmb]] – pMb - pig<br />
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| [[1lhs]] – stMb – sea turtle<br />
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| [[1mbs]] – Mb - seal<br />
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| [[1uvy]] – Mb – ''Paramecium caudatum''<br />
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| [[3qm5]], [[3qm6]] – btMb – blackfin tuna
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| === Mb mutants uncomplexed ===
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| [[3m38]], [[3m39]], [[3m3a]], [[3m3b]], [[3k9z]], [[3h57]], [[3h58]], [[2e2y]], [[2ef2]], [[2oh8]], [[2oh9]], [[2oha]], [[2ohb]], [[2blh]], [[2bli]], [[1h1x]], [[1co8]], [[1n9h]], [[1n9i]], [[1n9x]], [[1naz]], [[1f63]], [[1f65]], [[1dti]], [[1co9]], [[1cp0]], [[1cp5]], [[1cpw]], [[1ch1]], [[1ch2]], [[1ch3]], [[1ch5]], [[1ch7]], [[1ch9]], [[1cik]], [[1cio]], [[1ofk]], [[1ofj]], [[102m]], [[1obm]], [[2mbw]], [[1tes]], [[1irc]], [[1mti]], [[1mtj]], [[1mtk]], [[1mlf]], [[1mlg]], [[1mlh]], [[1mlj]], [[1mlk]], [[1mll]], [[1mlm]], [[1mlo]], [[1mlr]], [[1mln]], [[1mls]], [[2mga]], [[2mgb]], [[2mgc]], [[2mgd]], [[2mge]], [[2mgf]], [[2mgg]], [[2mgh]], [[2mgi]], [[2mgj]], [[2mgk]], [[2mgl]], [[2mgm]], [[2spl]], [[2spm]], [[2spn]], [[2spo]], [[1fcs]], [[1j52]], [[1lue]], [[1o16]], [[3ogb]], [[3obd]], [[3ock]], [[3sdn]], [[3o89]] - SwMb (mutant)<br />
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| [[2bwh]] - SwMb (mutant) – Laue<br />
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| [[3hc9]], [[3hen]], [[3heo]], [[3hep]], [[1nz2]], [[1nz3]], [[1rse]], [[1abs]], [[1xch]], [[1hrm]], [[1yma]], [[3rj6]] - hoMb (mutant) – horse<br />
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| [[2vlx]] , [[2vly]], [[2vlz]], [[2vm0]] – hoMb fragment<br />
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| [[1dm1]] – AlMb (mutant)<br />
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| [[2mm1]], [[3rgk]] – hMb (mutant) – human
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| === Mb containing a non-Fe protoporphyrin ===
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| [[1yog]], [[1yoh]], [[1yoi]], [[1myz]] – SwMb+Co protoporphyrin<br />
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| [[3mn0]] – SwMb (mutant)+Cu protoporphyrin+cyanide<br />
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| [[1j3f]] – SwMb+Cr salophen<br />
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| [[1ufj]], [[1ufp]] – SwMb (mutant)+Fe salophen<br />
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| [[2o58]], [[2o5b]] – hoMb+Mn protoporphyrin<br />
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| [[2o5l]] - hoMb+Mn protoporphyrin +methanol<br />
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| [[2o5m]] - hoMb+Mn protoporphyrin +azide<br />
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| [[2o5o]], [[2o5q]] - hoMb+Mn protoporphyrin +NO2<br />
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| [[2o5s]] - hoMb+Co protoporphyrin +NO2<br />
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| [[2o5t]] - hoMb+Co protoporphyrin<br />
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| [[3rjn]] - hoMb+Zn deuteroporphyrin
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| === Mb+NO ===
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| [[1jdo]], [[1mlu]] – SwMb+NO<br />
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| [[1hjt]] – SwMb (mutant)+NO<br />
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| [[2frj]], [[2frk]], [[1npf]] - hoMb+NO<br />
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| [[2nx0]] – BtMb+NO
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| === Mb+NO2 ===
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| [[2frf]], [[2fri]], [[3lr7]], [[3lr9]], [[3vau]] - hoMb+NO2
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| === Mb+O2 ===
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| [[1ltw]] - SwMb (mutant)+O2<br />
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| [[1a6m]], [[1mbo]], [[2z6s]], [[2z6t]] – SwMb+O2<br />
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| [[1mno]] - pMb (mutant)+O2
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| === Mb+CO ===
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| [[2bw9]], [[1mz0]] - SwMb (mutant)+CO – Laue<br />
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| [[2g0r]], [[2g0s]], [[2g0v]], [[2g0x]], [[2g0z]], [[2g10]], [[2g11]], [[2g12]], [[2g14]], [[2blj]], [[1dxc]], [[1dxd]], [[1do1]], [[1do3]], [[1do4]], [[1do7]], [[1abs]], [[1mcy]], [[1mbc]], [[3nml]] – SwMb (mutant)+CO<br />
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| [[1bzr]] , [[1a6g]], [[1ajg]], [[1ajh]], [[1spe]], [[1mym]], [[1mbc]] – SwMb+CO<br />
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| [[1myf]] - SwMb+CO – NMR<br />
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| [[2mb5]] - SwMb+CO – Neutron<br />
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| [[1dwr]], [[1dws]], [[1dwt]] – hoMb+CO<br />
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| [[1mdn]], [[1m6c]] – pMb (mutant)+CO <br />
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| [[1mwc]], [[1yca]] – pMb+CO<br />
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| [[3qm7]] – btMb + CO
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| ===Mb+OH===
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| [[1n9f]] – SwMb (mutant)+OH<br />
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| [[1gjn]] – hoMb+OH
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| === Mb+cyano compounds ===
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| [[2jho]] – SwMb cyanoMet<br />
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| [[3qm8]] - btMb cyanoMet<br />
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| [[1ebc]], [[2cmm]] - SwMb+cyanide<br />
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| [[1iop]] – SwMb+cyanide+hemin<br />
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| [[108m]], [[101m]], [[104m]], [[105m]], [[2myc]], [[2myd]], [[2mya]], [[2mye]], [[2myb]] – SwMb+isocyanides<br />
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| [[103m]], [[107m]], [[111m]], [[106m]], [[109m]], [[110m]], [[112m]] – SwMb (mutant) +isocyanides<br />
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| [[3ba2]] – hoMb+cyanide<br />
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| [[2fal]] – AlMb+cyanide<br />
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| [[2fam]] – AlMb+thiocyanate<br />
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| [[1lht]] – stMb+cyanide<br />
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| [[1emy]] – Mb+cyanide – asian elephant<br />
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| ===Mb + N3===
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| [[3qm9]] – btMb + N3
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| === MMb ===
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| [[1mgn]], [[1duk]] - SwMMb<br />
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| [[1duo]] – SwMMb+methyl-imidazole<br />
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| [[1myg]], [[1myh]], [[1myi]], [[1myj]], [[1ymb]] – pMMb<br />
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| [[1myt]] – MMb – yellowfin tuna
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| === Other complexes of Mb ===
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| [[3a2g]] – SwMb (mutant)+fluorescein<br />
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| [[2w6x]], [[2w6y]] - SwMb (mutant)+Xe<br />
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| [[2w6w]] - SwMb +Xe<br />
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| [[2eb8]], [[2eb9]] – SwMb+Cu<br />
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| [[3ase]] – SwMb + RuO3<br />
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| [[2ekt]], [[2eku]] – SwMb+methyl-depropionatehemin<br />
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| [[2d6c]] – SwMb+porphycene<br />
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| [[1swm]], [[1mbi]] – SwMb+imidazole<br />
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| [[1wvp]] – SwMb+tetrazolyl histidine<br />
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| [[2evk]] – SwMb (mutant)+acetic acid<br />
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| [[2evp]] - SwMb (mutant)+mercaptoethanol<br />
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| [[1v9q]] - SwMb (mutant)+Mn salophen derivative<br />
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| [[1dtm]] - SwMb (mutant)+4-methylimidazole<br />
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| [[2nsr]] – hoMb+nitro methane<br />
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| [[2nss]] - hoMb+nitro benzene<br />
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| [[1azi]] - hoMb+azide<br />
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| [[1bje]] – hoMb (mutant)+azide<br />
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| [[1nz4]] – hoMb (mutant)+Cd<br />
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| [[1nz5]] - hoMb (mutant)+Mn<br />
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| [[2in4]] - hoMb+Zn-DME<br />
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| [[1gjn]] – hoMb+hydroxide<br />
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| [[2nrm]] – BtMb S-nitrosylated<br />
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| [[5mba]] – AlMb+azide<br />
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| [[1mni]] – pMb+imidazole<br />
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| [[3qma]] - btMb+imidazole
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| === apo-Mb ===
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| [[1bvc]], [[1bvd]] – SwApo-Mb + biliverdin
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| ==External Resources== | | ==External Resources== |
| *{{Wikipedia|Myoglobin}} | | *{{Wikipedia|Myoglobin}} |
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| | == References == |
| | <references/> |
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| [[Category:Topic Page]] | | [[Category:Topic Page]] |