Effect of Copper(II) Ion Binding by Porin P1 Precursor Fragments from Fusobacterium nucleatum on DNA Degradation

Abstract

Fusobacterium nucleatum is one of the most notorious species involved in colorectal cancer. It was reported that numerous outer membrane proteins (OMP) are actively involved in carcinogenesis. In this paper, the structure and stability of certain complexes, as well as DNA cleavage and ROS generation by fragments of OMP, were investigated using experimental and theoretical methods. Mass spectrometry, potentiometry, UV-Vis, CD, EPR, gel electrophoresis and calculations at the density functional theory (DFT) level were applied. Two consecutive model peptides, Ac-AKGHEHQLE-NH2 and Ac-FGEHEHGRD-NH2, were studied. Both of these were rendered to form a variety of thermodynamically stable complexes with copper(II) ions. All of the complexes were stabilized, mainly due to interactions of metal with nitrogen and oxygen donor atoms, as well as rich hydrogen bond networks. It was also concluded that these complexes in the presence of hydrogen peroxide or ascorbic acid can effectively produce hydroxyl radicals and have an ability to cleave the DNA strands. Surprisingly, the second studied ligand at the micromolar concentration range causes overall DNA degradation.

Might Cu(ii) binding, DNA cleavage and radical production by YadA fragments be involved in the promotion ofF. nucleatumrelated cancers?

“…9 shows the competition for metal binding among different peptides constituting fragments of F. nucleatum outer-membrane proteins. The data for porin P1 precursor fragments, namely Ac-AKGHEHQLE-NH 2 and Ac-FGEHEHGRD-NH 2 , were already published 65 and are used herein only to prepare the competitive diagram of copper( ii ) speciation among peptides from F. nucleatum . It can be seen that complexes formed with the Ac-FGEHEHGRD-NH 2 peptide are the most abundant ones at pH 6.5.…”