What is the function of Hemerythrin?

Hemerythrin is a non-heme iron protein used by two phyla of marine invertebrates (sipunculids and brachiopods) for oxygen transfer and/or storage. It differs from the other oxygen-binding proteins (hemoglobin and hemocyanin) both in the polypeptide chain and in the metal complex used to reversibly bind dioxygen.

What is Hemerythrin made of?

Hemerythrin typically exists as a homooctamer or heterooctamer composed of α- and β-type subunits of 13–14 kDa each, although some species have dimeric, trimeric and tetrameric hemerythrins. Each subunit has a four-α-helix fold binding a binuclear iron centre.

What color is Hemerythrin?

Hemerythrin and myohemerythrin are essentially colorless when deoxygenated, but turn a violet-pink in the oxygenated state. Hemerythrin does not, as the name might suggest, contain a heme.

What animal has Hemerythrin?

Iron-containing, proteinaceous pigments, hemerythrins are present in the blood of certain bottom-dwelling marine worms (notably burrowing sipunculids) and of the brachiopod Lingula; the pigments serve as oxygen-carriers.

What is the oxidation state of Oxyhemerythrin?

The oxidation of oxyhemerythrin occurs via the deoxy species, little, if any, reactivity being attributable to the oxy form. The oxidation of the azide adduct of (semi-met)R is biphasic, in which in step one N3(-) is removed during the oxidation to methemerythrin, which in the second step recombines with N3(-).

Why does Hemerythrin have hydrophobic side chains?

Myohemerythrin has a similar structure to other hemerythrins which accounts for its oxygen binding and transporting functions. The hydrophobic environment of the core allows stabilization of the oxy adduct of myohemerythrin, preventing dioxygen from autoxidizing.

Where is Hemerythrin found?

Because of its size hemerythrin is usually found in cells or “corpuscles” in the blood rather than free floating. Unlike hemoglobin, most hemerythrins lack cooperative binding to oxygen making it roughly 1/4 as efficient as hemoglobin.

Is copper-based blood possible?

Unlike most animals on earth, whose blood is iron-based, some mollusks (Mollusca) and arthropods (Arthropoda) have copper-based blood. While the best-known example of an arthropod with copper-based blood is the horseshoe crab, a number of other arthropods have blue blood.

Where are hemocyanin found?

Hemocyanins are copper-containing respiratory pigments found in many mollusks (some bivalves, many gastropods, and cephalopods) and arthropods (many crustaceans, some arachnids, and the horseshoe crab, Limulus).

What is the function of hemerythrin?

Hemerythrin is an oligomeric protein responsible for oxygen transport in the marine invertebrate phyla of sipunculids, priapulids, brachiopods, and in a single annelid worm, magelona. Recently, hemerythrin was discovered in methanotrophic bacterium Methylococcus capsulatus.

What is the difference between heme and hemerythrin?

Hemerythrin does not, as the name might suggest, contain a heme. The names of the blood oxygen transporters hemoglobin, hemocyanin, hemerythrin, do not refer to the heme group (only found in globins), instead these names are derived from the Greek word for blood.

Why does hemerythrin/HHE have a low affinity for co?

Hemerythrin’s low affinity for CO poisoning reflects the role of hydrogen-bonding in the binding of O 2, a pathway mode that is incompatible with CO complexes which usually do not engage in hydrogen bonding. The hemerythrin/HHE cation-binding domain occurs as a duplicated domain in hemerythrins, myohemerythrins and related proteins.

How many subunits are in a hemehemerythrin?

Hemerythrin (molecular weight 107,000) contains eight subunits each of molecular weight 13,500. The protein binds iron which stabilizes the quaternary structure.

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