1 research outputs found
Ligation-Dependent Picosecond Dynamics in Human Hemoglobin As Revealed by Quasielastic Neutron Scattering
Hemoglobin,
the vital O<sub>2</sub> carrier in red blood cells,
has long served as a classic example of an allosteric protein. Although
high-resolution X-ray structural models are currently available for
both the deoxy tense (T) and fully liganded relaxed (R) states of
hemoglobin, much less is known about their dynamics, especially on
the picosecond to subnanosecond time scales. Here, we investigate
the picosecond dynamics of the deoxy and CO forms of human hemoglobin
using quasielastic neutron scattering under near physiological conditions
in order to extract the dynamics changes upon ligation. From the analysis
of the global motions, we found that whereas the apparent diffusion
coefficients of the deoxy form can be described by assuming translational
and rotational diffusion of a rigid body, those of the CO form need
to involve an additional contribution of internal large-scale motions.
We also found that the local dynamics in the deoxy and CO forms are
very similar in amplitude but are slightly lower in frequency in the
former than in the latter. Our results reveal the presence of rapid
large-scale motions in hemoglobin and further demonstrate that this
internal mobility is governed allosterically by the ligation state
of the heme group