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Heme Prosthetic Group definitions

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  • Heme
    Flat, disc-shaped structure composed of ferrous iron and protoporphyrin 9, enabling reversible oxygen binding in hemoglobin and myoglobin.
  • Prosthetic Group
    Non-protein component tightly integrated into a protein, essential for its biological function, such as oxygen binding in hemoglobin.
  • Myoglobin
    Oxygen-binding protein with a single subunit, utilizing a heme group for reversible oxygen interaction, lacking cooperative binding.
  • Hemoglobin
    Multisubunit oxygen transport protein, containing heme groups and exhibiting cooperative oxygen binding through conformational changes.
  • Ferrous Iron
    Central iron ion in heme, in the Fe2+ oxidation state, responsible for reversible oxygen binding and avoiding free radical formation.
  • Protoporphyrin 9
    Planar tetrapyrrole ring system surrounding iron in heme, providing structural support and facilitating non-covalent interactions.
  • Tetrapyrrole
    Ring system composed of four pyrrole rings, forming the backbone of protoporphyrin 9 in the heme structure.
  • Non-covalent Bond
    Interaction stabilizing heme within proteins, including hydrophobic, hydrogen, and ionic bonds, crucial for oxygen binding and protein structure.
  • Proximal Histidine
    Amino acid residue located below the heme plane, directly interacting with iron to stabilize its position within hemoglobin or myoglobin.
  • Distal Histidine
    Amino acid residue positioned above the heme plane, forming a hydrogen bond with bound oxygen to prevent iron oxidation and reduce CO toxicity.
  • Oxygen Affinity
    Capacity of hemoglobin or myoglobin to bind oxygen, determined by the heme group and influenced by protein conformation and interactions.
  • Ferric Iron
    Oxidized iron ion (Fe3+) in heme, unable to reversibly bind oxygen, often resulting from loss of stabilization by protein environment.
  • Carbon Monoxide
    Toxic molecule that binds heme iron more strongly than oxygen, blocking oxygen transport and causing cellular damage.
  • Positive Cooperativity
    Phenomenon in hemoglobin where oxygen binding to one subunit increases affinity in others, enhancing overall oxygen uptake.
  • Allosteric Protein
    Protein capable of conformational changes upon ligand binding, such as hemoglobin, enabling regulation of function and cooperative interactions.