Revisiting the concept of peptide bond planarity in an iron-sulfur protein by neutron structure analysis

The planarity of the peptide bond is important for the stability and structure formation of proteins. However, substantial distortion of peptide bonds has been reported in several high-resolution structures and computational analyses. To investigate the peptide bond planarity, including hydrogen atoms, we report a 1.2-angstrom resolution neutron structure of the oxidized form of high-potential iron-sulfur protein. This high-resolution neutron structure shows that the nucleus positions of the amide protons deviate from the peptide plane and shift toward the acceptors. The planarity of the H-N-C=O plane depends strongly on the pyramidalization of the nitrogen atom. Moreover, the orientation of the amide proton of Cys(75) is different in the reduced and oxidized states, possibly because of the electron storage capacity of the iron-sulfur cluster.

Automated summary

The planarity of the peptide bond is crucial for protein stability and structure formation. However, it has been observed that peptide bonds can be distorted. A high-resolution neutron structure analysis revealed that the position of the amide proton deviates from the peptide plane and shifts towards the acceptors. The planarity of the peptide bond depends on the pyramidalization of the nitrogen atom.