heme

Examples of heme in the following topics:

• Biosynthesis of Tetrapyrroles

  • One of the best-known porphyrins is heme, the pigment in red blood cells.
  • Heme is a cofactor of the protein hemoglobin.
  • Some iron-containing porphyrins are called hemes.
  • Heme-containing proteins, or hemoproteins, are found extensively in nature.
  • Bile pigments are the breakdown products of heme.

• Electron Transport Chain

  • Cytochrome proteins have a prosthetic heme group.
  • The heme molecule is similar to the heme in hemoglobin, but it carries electrons, not oxygen.
  • The heme molecules in the cytochromes have slightly different characteristics due to the effects of the different proteins binding them, which makes each complex.
  • This complex contains two heme groups (one in each of the cytochromes a and a3) and three copper ions (a pair of CuA and one CuB in cytochrome a3).

• Anaerobiosis and N2 Fixation

  • Interestingly, it is widely believed that leghemoglobin is the product of both the plant and the bacterium in which a protein precursor is produced by the plant and the heme (an iron atom bound in a porphyrin ring, which binds O2) is produced by the bacterium.
  • The protein and heme come together to function , allowing the bacteria to fix-nitrogen, giving the plant usable nitrogen and thus the plant provides the rhizobia a home.
  • The ribbons represent protein folds, while the conglomerate of spheres are the postion of the iron contain heme group which binds the oxygen.

• Biomolecules

  • Perhaps most famous are the tetradentate N4 macrocyclic ligands incorporated into the heme protein (most commonly seen as part of hemoglobin).
  • Heme B is a porphyrin (four linked pyrrole rings) that readily binds iron, as shown.

• Transport of Oxygen in the Blood

  • Each subunit surrounds a central heme group that contains iron and binds one oxygen molecule, allowing each hemoglobin molecule to bind four oxygen molecules.
  • Molecules with more oxygen bound to the heme groups are brighter red.
  • Hemoglobin is made up of four symmetrical subunits and four heme groups.
  • Iron associated with the heme binds oxygen.

• Jefferson, Slavery, and Race

  • As a widower, his father-in-law John Wayles had taken his mulatto slave Betty Hemings as a concubine and had six children with her during his last 12 years.
  • Betty Hemings' descendants were trained and assigned to domestic service and highly skilled artisan positions at Monticello; none worked in the fields.
  • Since about 2000, historians have widely believed that the widower Jefferson started a sexual relationship with Sally Hemings while in Paris.
  • Onuf suggested that this was because of Jefferson's concerns of his unacknowledged "shadow family" with Sally Hemings.

• RBC Physiology

  • Each hemoglobin molecule contains four iron-binding heme groups, which are the site of oxygen (O2) binding.
  • The heme groups are the green structures nestled among the alpha and beta.

• Some Polycyclic Heterocycles

  • Porphyrin is an important cyclic tertrapyrrole that is the core structure of heme and chlorophyll.

• ABC Transporters

  • In bacterial efflux systems, certain substances that need to be extruded from the cell include surface components of the bacterial cell (e.g. capsular polysaccharides, lipopolysaccharides, and teichoic acid), proteins involved in bacterial pathogenesis (e.g. hemolysis, heme-binding protein, and alkaline protease), heme, hydrolytic enzymes, S-layer proteins, competence factors, toxins, antibiotics, bacteriocins, peptide antibiotics, drugs and siderophores.

• Energy Requirements

  • Myoglobin is similar to hemoglobin in that it contains a heme group (an oxygen binding site).
  • The heme component of myoglobin, shown in orange, binds oxygen.