Article ID Journal Published Year Pages File Type
442964 Journal of Molecular Graphics and Modelling 2009 9 Pages PDF
Abstract

We studied the terahertz (THz) spectroscopy and low frequency normal modes of both apo- and holo- (adenosine monophosphate (AMP)-bound) ricin-A-chain (RTA) as a means to understand the dynamical changes that RTA undergoes upon substrate binding. The calculated THz spectra of apo- and holo-RTAs demonstrated a general intensity suppression upon substrate binding, which is attributed to the reduced number of collective motion in THz region. In normal mode analysis of RTA we find a shearing motion that is shared by both the apo- and holo-RTAs, whereas a breathing motion, and an upward hinge rising and an α-G bending characteristic motion are dampened significantly upon AMP binding, suggesting these motions are involved in the necessary flexibility of the active site. In contrast, we find a normal mode motion that separates domains I and II of RTA at the interface that is more common in the holo-protein. We hypothesized that the flexibility of the entrance of RTA can facilitate the entry of rRNA and allow the substrate to adjust its conformation and orientation prior to depurination. This process suggests an rRNA binding pathway which is supplemental the current RTA depurination mechanism.

Related Topics
Physical Sciences and Engineering Chemistry Physical and Theoretical Chemistry
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