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Talk- Noriko Inoguchi

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  • cmb seminar
When Jun 07, 2017
from 12:00 PM to 01:00 PM
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Studies of molecular mechanism of oxygen-binding affinity difference in deer mouse hemoglobin


Hemoglobin is a heterotetrameric oxygen-transporting protein. It has two distinct conformational states, one of them is called deoxygenated or Tense (T) state, and the other is called oxygenated or Relaxed (R) state.  The binding of an oxygen molecule to the heme triggers tertiary level conformational changes, leading to quaternary level changes.

The focus of this study is understanding molecular mechanism of oxygen-binding differences observed in deer mice. Deer mice live over a wider range of altitudes, and the mice living at highland (approximately 4000 m above the sea level) have hemoglobin with a higher oxygen-binding affinity than those living at lowland (approximately 1500 m above the sea level).  Sequence comparisons reveal twelve amino acid substitutions, and only 5 of them are chemically different residues.


n order to elucidate the mechanism of such functional differences, recombinant deer mouse hemoglobin of highland and lowland were expressed, and their X-ray crystal structures were compared. The structures showed that large carbon alpha displacements in the loop region near heme pocket of the alpha subunit due to Pro50His substitution. Also, highland hemoglobin has R state-like inter subunit packing while lowland hemoglobin has T state-like intersubunit packing. 

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