hemoglobin

Hemoglobin (also spelled haemoglobin and abbreviated Hb or Hgb) is the iron-containing oxygen-transport metalloprotein in the red blood cells of vertebrates.

In mammals, the protein makes up about 97% of the red cell’s dry content, and around 35% of the total content (including water).

Hemoglobin transports oxygen from the lungs or gills to the rest of the body, such as to the muscles, where it releases the oxygen for cell use.

It also has a variety of other roles of gas transport and effect-modulation which vary from species to species, and are quite diverse in some invertebrates.

Structure

In most humans, the haemoglobin molecule is an assembly of four globular protein subunits (the globin molecules).

Each subunit is composed of a protein chain tightly associated with a non-protein heme group.

Each protein chain arranges into a set of alpha-helix structural segments connected together in a globin fold arrangement, so called because this arrangement is the same folding motif used in other heme/globin proteins such as myoglobin.

This folding pattern contains a pocket which strongly binds the heme group.

See also

 myoglobin