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- Created 2012-04-13
) is a nitrogen or oxygen carrier, because naturally occurring oxygen and nitrogen interact similarly with this protein; and a
found in the
root nodules of
plants. It is produced by legumes in response to the roots being colonized by nitrogen-fixing bacteria, termed
, as part of the
interaction between plant and bacterium: roots uninfected with
do not synthesise leghemoglobin. Leghemoglobin has close chemical and structural similarities to
, and, like hemoglobin, is red in colour. The holoprotein (protein + heme cofactor) is widely believed to be a product of both
in which the apoprotein is produced by the plant and the
(an iron atom bound in a
ring) is produced by the
. There is some evidence however suggesting that the heme moiety is also produced by the plant.
In plants infected with
, (such as
s), the presence of
in the root nodules would reduce the activity of the oxygen-sensitive
- an enzyme responsible for the fixation of atmospheric nitrogen. Leghemoglobin buffers the concentration of free
of infected plant cells to ensure the proper function of root nodules. Leghemoglobin has a high affinity for oxygen (a
of about 0.01 µM), about ten times higher than the β chain of human hemoglobin. This allows an oxygen concentration that is low enough to allow nitrogenase to function but high enough so that it can provide the bacteria with oxygen for respiration.
Although leghemoglobin was once thought to provide a buffer for nodule oxygen, recent studies indicate that it stores only enough oxygen to support nodule
for a few seconds. Its function is to help provide oxygen to the respiring symbiotic bacterial cells in a manner analogous to hemoglobin transporting oxygen to respiring tissues in animals.
Other plants, like
which is an
, produce a hemoglobin in their symbiotic root nodules.
from Wikipedia (last updated: 19 May), licensed under
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Chemistry of leghaemoglobin
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