Theoretical Studies of Interactions between O‑Phosphorylated
and Standard Amino-Acid Side-Chain Models in Water
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Abstract
Phosphorylation
is a common post-translational modification of
the amino-acid side chains (serine, tyrosine, and threonine) that
contain hydroxyl groups. The transfer of the negatively charged phosphate
group from an ATP molecule to such amino-acid side chains leads to
changes in the local conformations of proteins and the pattern of
interactions with other amino-acid side-chains. A convenient characteristic
of the side chain–side chain interactions in the context of
an aqueous environment is the potential of mean force (PMF) in water.
A series of umbrella-sampling molecular dynamic (MD) simulations with
the AMBER force field were carried out for pairs of O-phosphorylated
serine (pSer), threonine (pThr), and tyrosine, (pTyr) with natural
amino acids in a TIP3P water model as a solvent at 298 K. The weighted-histogram
analysis method was used to calculate the four-dimensional potentials
of mean force. The results demonstrate that the positions and depths
of the contact minima and the positions and heights of the desolvation
maxima, including their dependence on the relative orientation depend
on the character of the interacting pairs. More distinct minima are
observed for oppositely charged pairs such as, e.g., O-phosphorylated
side-chains and positively charged ones, such as the side-chains of
lysine and arginine