4HHB - Introduction
Human deoxyhaemoglobin transports oxygen in the blood throughout the body.
Human deoxyhaemoglobin is an iron containing protein in red blood cells (erythrocytes)
that reversibly binds oxygen. Each cubic millimeter of human blood contains
5 to 6 million red cells and there are about 25 trillion of these cells in
the body’s 5L of blood. The red cell contains about 250 million molecules
of hemoglobin. Hemoglobin binds the gaseous molecule nitric oxide (NO) as
well as oxygen. As red blood cells pass through the capillary beds of the
lungs and other respiratory organs, oxygen diffuses into the erythrocytes
and hemoglobin binds oxygen. Hemoglobin unloads the carried oxygen in the
capillaries of systemic circuit. There the oxygen diffuses into body cells.
The NO relaxes the walls of the capillaries, allowing them to expand, an
effect that helps deliver oxygen to the cells.
Structurally, hemoglobin is a gobular protein built of 4 subunits (tetramers)
with 4 hemes (iron-containing coenzymes). The structure was determined by
X-Ray Diffraction to a resolution of 1.74 Anstroms and an R-value of 0.135.
The 4 polymer chains contain a total of 574 residues and 4779 atoms. 4HHB
contains 2 HET groups – HEM (PROTOPORPHYRIN IX CONTAINING FE) and the PO4
PHOSPHATE ION.
Sources:
CBI PubMed - indexed for MEDLINE
“Biology” by Campbell, Reece, and Mitchell