Correlation map for the cross-correlations Cij between the motions of the residues.
The two axes refer to residue indices.
The regions colored magenta, blue, brown and orange refer to strongly
correlated, correlated (Cij
> 0), uncorrelated (Cij» 0) and anticorrelated (Cij
< 0) pairs, respectively. The subunits are indicated by the bars
parallel to the axes. Blue blocks indicate positively correlated units
(intrasubunit correlations for a1,
b1,
a2 and
b2 domains) and
the off-diagonal encircled (by red ellipses) blue regions indicate the
interdomain correlations between subunits
a1 (or
a2) and
b1 (or
b2).
Anticorrelated (concerted but opposite direction) motions are observed
for the subunit pair a1-
a2, as well as the pair
b1-
b2. Results are presented for 1a3n. 1bbb and 1hho
showed similar behavior.
Energy surface in the close neighborhood of the original structure, shown for (a) the T form, and (b) the R2 form of the Hb tetramer.
p align="justify">The ordinate represents the
conformational energy estimated from pairwise addition of the
Miyazawa-Jernigan inter-residue contact potentials for all pairs of
residues whose a-carbons are
located within rc = 6.5 Å .
The abscissa refers to
different conformations generated by rescaling the extent of
deformation predicted by the ANM. Quantitatively, these conformations
are generated by adding to the original residue position vectors the
fluctuation vectors, multiplied by the scaling factor indicated along
the abscissa. We note that one of the fluctuation directions,
indicated by the arrow, is more favorable. These directions exactly
coincide with that of the global reconfiguration in the T
ßà
R2 transition.
Comparison of the T (left), R2 (middle) and reconfigured T (right) forms of Hb.
The T and R2 forms refer to the PDB
structures deoxy-Hb and CO-bound Hb. The reconfigured T is predicted
using scaling factor 4. We started from the T form and compute its
most probable global change using ANM. Note the similarity between the
relaxed form predicted by our computations (bottom) and the
experimental R2 form (middle) (rms deviation 2.32 Å).
