Oxygen Transport & Storage Proteins

This flashcard set covers the structure, function, evolutionary history, and clinical disorders related to oxygen transport and storage proteins like hemoglobin and myoglobin.

Haeme (Heme)

An organic, ring-shaped porphyrin molecule made from 4 pyrroles (tetrapyrrole) capable of hosting an iron molecule.

Hemocyanin

A blue oxygen-transport protein containing copper, found in spiders, crustaceans, octopuses, and squids.

Chlorocruorin

A green oxygen-transport protein containing iron, found in some segmented worms, leeches, and marine worms.

Hemerythrin

A violet oxygen-transport protein containing iron, found in marine worms including peanut worms and brachiopods.

Vanabin

A yellow protein containing vanadium, found in beetles, sea squirts, and sea cucumbers.

Chromosome 16

The location of the adult and embryonic $\alpha$-globin genes ($\zeta$, $\alpha 2$, $\alpha 1$) in humans.

Chromosome 11

The location of the $\beta$-globin gene cluster, including $\epsilon$, $\gamma$, $\delta$, and $\beta$ genes.

Cytoglobin

A globin expressed in adventitial fibroblasts, cardiomyocytes, and smooth muscle, with a hexa-coordinate iron atom coordination.

Neuroglobin

A globin protein found in sympathetic nerves with a hexa-coordinate iron atom coordination.

Myoglobin (Mb)

A single polypeptide of $153$ amino acids with one haeme group, found in cardiomyocytes and smooth muscle for oxygen transport and storage.

Proximal Histidine (His F8)

Also known as $\text{His93}$, this is the residue coordinated directly to the haeme iron group.

Distal Histidine (His E7)

A residue that establishes a hydrogen bond with $O_2$ and assists in discriminating between ligands like $CO$ and $O_2$.

Globin Fold

A structure built by $\alpha$-helices that provides a deep hydrophobic crevice (mainly helices E, F, and G) where haeme is bound.

High-spin $Fe^{2+}$

The state of the iron in the ferrous form (deoxymyoglobin) where it is five-coordinate and lies about $60\,pm$ above the porphyrin plane.

Hemoglobin (Hb)

A tetramer consisting of four subunits and four haeme groups, localized in red blood cells for oxygen transport and delivery.

Association Constant ($K_a$)

The equilibrium constant representing the measure of affinity between a protein and a ligand, defined as $[PL] / ([P][L])$; high values indicate high affinity.

Sigmoidal Binding Curve

The characteristic shape of the hemoglobin oxygen-binding curve, indicating cooperative binding properties.

Thalassemias

A heterogeneous group of autosomal recessive genetic disorders characterized by decreased or absent synthesis of globin chains.

Hydrops Fetalis

The most severe form of $\alpha$-thalassemia (genotype $- - / - -$) which is incompatible with extrauterine life.

Cooley's Anemia

Also known as $\beta$-thalassemia major (genotype $- / -$), it involves a total lack of $\beta$-globin chain production.