Biomedical Engineering Reference
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Figure 10.21
Poisson-Boltzmann electrostatic surface charges in the complex of
DnaK(1-605) and DnaJ(1-70). The surface charges are contoured
between 28 kT (red) and +8 kT (blue). The figure was prepared in
Pymol, using the PB-plug-in written by Carlson and Delano. 17 The
location of the spin-labels V210C-MTSL, D326C-MTSL and T417C-
MTSL are indicated. Adapted from ref. 32.
A patch of electrostatic interactions is likely unspecific enough to provide
sufficient binding enthalpy for the ligand, even when it is moving around quite
significantly. This binding mode would preserve entropy in both ligand and
protein. One may expect that interfaces consisting of contiguous apolar
(hydrophobic) residues would have the same dynamic capability. Of course,if
those surfaces were exposed, they would likely cause aggregation and wouldbe
selected against. A contiguous protected, hydrophobic surface exists in the
substrate binding cleft the Hsp70s—it would not be surprising if the apolar
ligands in this chaperone system remain dynamic as well. Clearly, inter-
molecular interfaces featuring complementary hydrogen bonds and/or precise
steric fits will not be dynamic.
Acknowledgements
The work in Sections 10.2 and 10.3 was part of my thesis research at the
University of Nijmegen, the Netherlands, under guidance of Drs Cees W.
Hilbers and Simon de Bruin (deceased) and supported by a fellowship to
ERPZ from the Netherlands Organization for Scientific Research. The work in
Section 10.3 involved Saumen Chakraborty and Vince L. Pecoraro at the
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