Cross-Correlated Motions in Azidolysozyme

TL;DR

This study investigates how attaching azide groups to specific alanine residues in lysozyme affects the protein's local and global dynamics, revealing site-dependent changes detectable through spectroscopic methods.

Contribution

It provides a quantitative analysis of how azide labelling alters protein dynamics at different sites, highlighting the importance of residue location.

Findings

Minimal dynamic change at Ala92 upon azide attachment

Pronounced changes at Ala90 in cross-correlated motions

Spectroscopic differences distinguish attachment sites

Abstract

The changes in the local and global dynamics of azide-labelled Lysozyme compared with that of the wild type protein are quantitatively assessed for all alanine residues along the polypeptide chain. Although attaching -N$_3$ to alanine residues has been considered to be a minimally invasive change in the protein it is found that depending on the location of the Alanine residue the local and global changes in the dynamics differ. For Ala92 the change in the cross correlated motions are minimal whereas attaching -N$_3$ to Ala90 leads to pronounced differences in the local and global correlations as quantified by cross correlation coefficients of the C$_{\alpha}$ atoms. It is also demonstrated that the spectral region of the asymmetric azide stretch distinguishes between alanine attachment sites whereas changes in the low frequency, far-infrared region are less characteristic.