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PDBsum entry 4avd
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Oxygen transport
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PDB id
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4avd
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References listed in PDB file
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Key reference
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Title
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High resolution crystal structures of the cerebratulus lacteus mini-Hb in the unligated and carbomonoxy states.
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Authors
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F.Germani,
A.Pesce,
A.Venturini,
L.Moens,
M.Bolognesi,
S.Dewilde,
M.Nardini.
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Ref.
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Int J Mol Sci, 2012,
13,
8025-8037.
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PubMed id
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Abstract
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The nerve tissue mini-hemoglobin from Cerebratulus lacteus (CerHb) displays an
essential globin fold hosting a protein matrix tunnel held to allow traffic of
small ligands to and from the heme. CerHb heme pocket hosts the distal
TyrB10/GlnE7 pair, normally linked to low rates of O(2) dissociation and
ultra-high O(2) affinity. However, CerHb affinity for O(2) is similar to that of
mammalian myoglobins, due to a dynamic equilibrium between high and low affinity
states driven by the ability of ThrE11 to orient the TyrB10 OH group relative to
the heme ligand. We present here the high resolution crystal structures of CerHb
in the unligated and carbomonoxy states. Although CO binds to the heme with an
orientation different from the O(2) ligand, the overall binding schemes for CO
and O(2) are essentially the same, both ligands being stabilized through a
network of hydrogen bonds based on TyrB10, GlnE7, and ThrE11. No dramatic
protein structural changes are needed to support binding of the ligands, which
can freely reach the heme distal site through the apolar tunnel. A lack of main
conformational changes between the heme-unligated and -ligated states grants
stability to the folded mini-Hb and is a prerequisite for fast ligand diffusion
to/from the heme.
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