Analysis of O2 -binding Sites in Proteins Using Gas-Pressure NMR Spectroscopy: Outer Surface Protein A

Biophysical Journal
Takahiro KawamuraRyo Kitahara

Abstract

Internal cavities in proteins produce conformational fluctuations and enable the binding of small ligands. Here, we report a NMR analysis of O2-binding sites by O2-induced paramagnetic relaxation enhancements (PREs) on amide groups of proteins in solution. Outer surface protein A contains a nonglobular single-layer β-sheet that connects the N- and C-terminal globular domains. Several cavities have been observed in both domains of the crystallized protein structure. The receptor-binding sites are occluded and line the largest cavity of the C-terminal domain. We observed significant O2-induced PREs for amide protons located around the largest cavity and at the central β-sheet. We suggested three potential O2-accessible sites in the protein based on the 1/r6 distance dependence of the PRE. Two sites were in or close to the largest cavity and the third site was in the surface crevice of the central β-sheet. These results provide, to our knowledge, the first evidence of ligand binding to the surface crevice and cavity of the protein in solution. Because O2 generally binds more specifically to hydrophobic rather than hydrophilic cavities within a protein, the results also indicated that the receptor-binding sites lining the largest c...Continue Reading

Citations

Oct 2, 2019·Proceedings of the National Academy of Sciences of the United States of America·Mengjun XueFrans A A Mulder
Dec 23, 2017·Protein Science : a Publication of the Protein Society·Ryo KitaharaFrans A A Mulder

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