Hemerythrin

From Academic Kids

Missing image
Hemerythrin.jpg
Single Oxygenated Hemerythrin protein
Missing image
HemerythrinTri.jpg
Trimeric Hemerythrin Protein Complex

Hemerythrin is a protein responsible for oxygen transportation in the marine invertebrate phyla of sipuniculids, priapulids, brachiopods, and in a single annelid worm, magelona. It is essentially colorless when deoxygenated, but turns a violet-pink in the oxygenated state.

Hemerythrin is not, as the name might suggest, a heme. The "heme" was at first applied to any oxygen-carrying proteins, such as hemoglobin, and when hemoglobin was analyzed, the heme structure was named for the iron-porphyrin cofactor in the transport protein (globin being a general term for a globular protein). Later, after hemerythrin was named, it was discovered that not every oxygen-carrying protein has a heme prosthetic group.

As it turns out the oxygen binding site is a binuclear iron center. The iron atoms are coordinated to the protein through the carboxylate side chains of a glutamate and aspartate, and five histidine peptides. When oxygenated the iron atoms are bridged by a μ-oxo bridge. When deoxygenated the iron atoms are bridged by a hydroxyl group. When binding a oxygen molecule the hydrogen atom from the hydroxyl bridged moves over onto the bound ligand. When releasing the oxygen molecule, the mu-oxo bridge retrieves the hydrogen atom and returns to a hydroxyl group. Thus the following:

Fe-OH-Fe + O2 <-> Fe-O-Fe-O2 + H+

Hemerythrin affinity for Carbon Monoxide (CO) is actually lower then its affinity for Oxygen (O2) (unlike hemoglobin which has a very high affinity for CO) making Hemerythrin immune to CO poisoning.

Most Hemorythrin lacks Cooperative binding to oxygen (unlike Hemoglobin) making it roughly 1/4 as efficient as Hemoglobin. In some brachiopods though, hemerythrin shows cooperative binding of oxygen. Cooperative binding is achieved by cooperation between subunits: when one subunit becomes oxygenated it increases the affinity for oxygen of the other subunits in the complex.

Hemorythrin is a small protein made of 2-8 identical subunit protiens about 13.5kD in size, totaling 108 kD (if 8 units). 8 subunits or "octamer" form is most common, though some species have 2,3 and 4 subunit groupings. Each subunit carries 2 iron atoms bond together, that can bind to one oxygen molecule. Because of its size Hemorythrin is usually found in cells or "corpuscles" in the blood rather then free floating.

Navigation

Academic Kids Menu

  • Art and Cultures
    • Art (http://www.academickids.com/encyclopedia/index.php/Art)
    • Architecture (http://www.academickids.com/encyclopedia/index.php/Architecture)
    • Cultures (http://www.academickids.com/encyclopedia/index.php/Cultures)
    • Music (http://www.academickids.com/encyclopedia/index.php/Music)
    • Musical Instruments (http://academickids.com/encyclopedia/index.php/List_of_musical_instruments)
  • Biographies (http://www.academickids.com/encyclopedia/index.php/Biographies)
  • Clipart (http://www.academickids.com/encyclopedia/index.php/Clipart)
  • Geography (http://www.academickids.com/encyclopedia/index.php/Geography)
    • Countries of the World (http://www.academickids.com/encyclopedia/index.php/Countries)
    • Maps (http://www.academickids.com/encyclopedia/index.php/Maps)
    • Flags (http://www.academickids.com/encyclopedia/index.php/Flags)
    • Continents (http://www.academickids.com/encyclopedia/index.php/Continents)
  • History (http://www.academickids.com/encyclopedia/index.php/History)
    • Ancient Civilizations (http://www.academickids.com/encyclopedia/index.php/Ancient_Civilizations)
    • Industrial Revolution (http://www.academickids.com/encyclopedia/index.php/Industrial_Revolution)
    • Middle Ages (http://www.academickids.com/encyclopedia/index.php/Middle_Ages)
    • Prehistory (http://www.academickids.com/encyclopedia/index.php/Prehistory)
    • Renaissance (http://www.academickids.com/encyclopedia/index.php/Renaissance)
    • Timelines (http://www.academickids.com/encyclopedia/index.php/Timelines)
    • United States (http://www.academickids.com/encyclopedia/index.php/United_States)
    • Wars (http://www.academickids.com/encyclopedia/index.php/Wars)
    • World History (http://www.academickids.com/encyclopedia/index.php/History_of_the_world)
  • Human Body (http://www.academickids.com/encyclopedia/index.php/Human_Body)
  • Mathematics (http://www.academickids.com/encyclopedia/index.php/Mathematics)
  • Reference (http://www.academickids.com/encyclopedia/index.php/Reference)
  • Science (http://www.academickids.com/encyclopedia/index.php/Science)
    • Animals (http://www.academickids.com/encyclopedia/index.php/Animals)
    • Aviation (http://www.academickids.com/encyclopedia/index.php/Aviation)
    • Dinosaurs (http://www.academickids.com/encyclopedia/index.php/Dinosaurs)
    • Earth (http://www.academickids.com/encyclopedia/index.php/Earth)
    • Inventions (http://www.academickids.com/encyclopedia/index.php/Inventions)
    • Physical Science (http://www.academickids.com/encyclopedia/index.php/Physical_Science)
    • Plants (http://www.academickids.com/encyclopedia/index.php/Plants)
    • Scientists (http://www.academickids.com/encyclopedia/index.php/Scientists)
  • Social Studies (http://www.academickids.com/encyclopedia/index.php/Social_Studies)
    • Anthropology (http://www.academickids.com/encyclopedia/index.php/Anthropology)
    • Economics (http://www.academickids.com/encyclopedia/index.php/Economics)
    • Government (http://www.academickids.com/encyclopedia/index.php/Government)
    • Religion (http://www.academickids.com/encyclopedia/index.php/Religion)
    • Holidays (http://www.academickids.com/encyclopedia/index.php/Holidays)
  • Space and Astronomy
    • Solar System (http://www.academickids.com/encyclopedia/index.php/Solar_System)
    • Planets (http://www.academickids.com/encyclopedia/index.php/Planets)
  • Sports (http://www.academickids.com/encyclopedia/index.php/Sports)
  • Timelines (http://www.academickids.com/encyclopedia/index.php/Timelines)
  • Weather (http://www.academickids.com/encyclopedia/index.php/Weather)
  • US States (http://www.academickids.com/encyclopedia/index.php/US_States)

Information

  • Home Page (http://academickids.com/encyclopedia/index.php)
  • Contact Us (http://www.academickids.com/encyclopedia/index.php/Contactus)

  • Clip Art (http://classroomclipart.com)
Toolbox
Personal tools