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Myoglobin and Hemoglobin v2

Myoglobin (Mb) is a monomer that stores oxygen in tissues, while Hemoglobin (Hb) is a tetramer that transports oxygen from the lungs to tissues. Both proteins utilize a heme group for oxygen binding, with their structures evolved to prevent the oxidation of ferrous iron (Fe2+) to ferric iron (Fe3+), ensuring reversible oxygen binding. The document highlights the distinct functions and structural differences between Mb and Hb in oxygen transport.

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6 views6 pages

Myoglobin and Hemoglobin v2

Myoglobin (Mb) is a monomer that stores oxygen in tissues, while Hemoglobin (Hb) is a tetramer that transports oxygen from the lungs to tissues. Both proteins utilize a heme group for oxygen binding, with their structures evolved to prevent the oxidation of ferrous iron (Fe2+) to ferric iron (Fe3+), ensuring reversible oxygen binding. The document highlights the distinct functions and structural differences between Mb and Hb in oxygen transport.

Uploaded by

zao
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Oxygen Transport

Hemoglobin
Myoglobin (Mb) has a single binding site for
heme and oxygen

• 153 amino acid protein

• All a-helical (A –H)

• O2 binding is facilitated by
a heme group (brown).

• Heme is tucked between


helices E and F
Oxygen Transport

• Myoglobin (Mb) functions


as a monomer and is used
for O2 storage in tissues.

Hemoglobin
Oxygen Transport

• Myoglobin (Mb) functions


as a monomer and is used
for O2 storage in tissues.

• Hemoglobin (Hb) functions


as a tetramer of Mb-like
subunits. Hb is used to Hemoglobin
transport O2 from the lungs
to tissues.
Heme is used by oxygen-binding proteins

• No amino acid side chains


can reversibly bind O2.

• Porphyrin ring with a ferrous


iron (Fe2+) coordinated in
the center.

• Porphyrin ring is planar.

• Heme binding pocket Mb


prevents oxidation of ferrous
Fe2+ (which reversibly binds
O2) to ferric Fe3+ (which
does not bind O2).
Summary

Myoglobin (Mb) and Hemoglobin (Hb):


Both Mb and Hb bind O2 using the heme group, but the function of
each molecule is different.

* Mb is monomer and stores O2 in tissues.

* Hb is tertramer (2a + 2b) of 4 Mb-like subunits. Unlike Mb, Hb


transports O2 from lungs to tissue.

* The environment of the heme in both Hb and Mb evolved to


prevent oxidation from Fe2+ to Fe 3+, and thus allows reversible
O2 binding.

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