Heme and heme protiens, myoglobin (muscle) and hemoglobin (blood)

(Under construction)

Image developed by T. Mallow 12/28/2007 via Cn3D FASTA file import. View shows the proximal histidine coordinating the Fe atom at the center of the heme porphyrin ring. Opposite the proximal histidine is a nearby distal histidine that coordinates the binding of the Fe at the center of the heme with oxygen during myoglobin's oxygenated state. However, this view shows a carbonmononoxy- pair bound to the Fe in the cleft normally used to bind oxygen. A significant thing to know is that molecules such as carbon monoxide can bind to this oxygen binding site with the net effect of lowering O2 saturation or O2 concentrations delivered to tissues. This hypoxic state is always the case when smokers breath in combustion products from tobacco such as CO. 

Query: myoglobin [Homo sapiens]
[gi: 44955885]
Structure: 1AJ9 Chain A, R-State Human Carbonmonoxyhemoglobin Alpha-A53s
Reference: [MMDB] [PubMed]

Directory

Myoglobin structure, primary, secondary, tertiary
Hemoglobin tructure, primary, secondary, tertiary, quaternary
Porphyrin structure and heme forms

Fe oxidation states in the porphyrin heme group of myoglobin

Fe+2    ferrous, state in which oxygen will bind with iron; in this state, the molecule is deoxymyoglobin
Fe+3    ferric, state to which oxygen is already bound; hence no further binding, this is oxymyoglobin
Fe+4    rare in nature

Oxygenation and deoxygenation, blood gas and tissue chemistry, CO2 dissociation curves, O2 binding in lungs and release at tissues, left and right shift, Bohr shift.

 

Noted citations and/or abstracts

Strong iron demand during hypoxia-induced erythropoiesis is associated with down-regulation of iron-related proteins and myoglobin in human skeletal muscle

Robach P, Cairo G, Gelfi C, Bernuzzi F, Pilegaard H, Viganň A, Santambrogio P, Cerretelli P, Calbet JA, Moutereau S, Lundby C.

Département médical, Ecole Nationale de Ski et d'Alpinisme, Chamonix, France.

Iron is essential for oxygen transport because it is incorporated in the heme of the oxygen-binding proteins hemoglobin and myoglobin. An interaction between iron homeostasis and oxygen regulation is further suggested during hypoxia, in which hemoglobin and myoglobin syntheses have been reported to increase. This study gives new insights into the changes in iron content and iron-oxygen interactions during enhanced erythropoiesis by simultaneously analyzing blood and muscle samples in humans exposed to 7 to 9 days of high altitude hypoxia (HA). HA up-regulates iron acquisition by erythroid cells, mobilizes body iron, and increases hemoglobin concentration. However, contrary to our hypothesis that muscle iron proteins and myoglobin would also be up-regulated during HA, this study shows that HA lowers myoglobin expression by 35% and down-regulates iron-related proteins in skeletal muscle, as evidenced by decreases in L-ferritin (43%), transferrin receptor (TfR; 50%), and total iron content (37%). This parallel decrease in L-ferritin and TfR in HA occurs independently of increased hypoxia-inducible factor 1 (HIF-1) mRNA levels and unchanged binding activity of iron regulatory proteins, but concurrently with increased ferroportin mRNA levels, suggesting enhanced iron export. Thus, in HA, the elevated iron requirement associated with enhanced erythropoiesis presumably elicits iron mobilization and myoglobin down-modulation, suggesting an altered muscle oxygen homeostasis.

PMID: 17311997 [PubMed - indexed for MEDLINE]