Coordination pattern and reactivity of two model peptides from porin protein P1

A voltammetric peptide biosensor for Cu2+ metal ion quantification in coffee seeds

A prion-derived copper(II)-binding peptide was assembled onto a gold electrode for the building of a voltammetric biosensor for measuring the Cu2+ metal ion in biological samples. The chosen sequence was H-CVNITKQHTVTTTT-NH2, with an appended cysteine residue for binding to the gold surface as a self-assembled monolayer and a histidine residue as the anchorage point for copper(II) complexation. The biosensor showed a linear range of 10-7 to 10-6 M with an 8.0 × 10-8 M detection limit and a 1.0 × 10-7 M quantification limit, with good precision, trueness, and absence of matrix effect. The quantification of Cu2+ was performed in the presence of other transition metal ions, such as Zn2+, Cd2+, Fe2+, or Ni2+, which indicates the excellent selectivity of the biosensor. When the modified electrode was applied for measuring copper(II) in calcined coffee seeds, a difference in copper amount was observed between two Coffea arabica cultivars that were submitted to a treatment with a copper-based antifungal, showing the applicability of the biosensor in the agricultural field.

Can bacteria F. nucleatum be actively involved in colon cancer progression via a radical mediated mechanism?

Outer membrane proteins of Fusobacterium nucleatum, a cancer‑leading bacteria, are considered as the factors responsible for its pathogenicity. Among them, homotrimeric autotransporter protein YadA (Yersinia adhesin A) is an important virulence factor also found in the outer membrane of pathogenic Yersinia species. In this paper, the structure and stability of certain Cu(II) complexes with YadA fragments were investigated using both, experimental and theoretical methods. Potentiometry, UV-Vis, CD, EPR, and calculations at the density functional theory (DFT) level were applied to determine the metal ion coordination sphere. Moreover, the complexes ability to DNA cleavage and reactive oxygen species (ROS) production was studied. We have shown that copper(II) complexes can cleave DNA by 1O2, O2•- and •OH, which are formed in the studied systems. However, the results of electrophoretic experiments revealed that complexes cleave DNA less effectively than free copper(II) ions. Therefore, the presence of studied peptides may prevent DNA from a Cu(II)-induced damage to some extent.

May Cu(II) binding, DNA cleavage and radicals production by YadA fragments be involved in the promotion of F. nucleatum related cancers?

In many cases, human microbiota is associated with cancer progression. It was concluded that Fusobacterium nucleatum increases neoplastic changes. This bacterium is naturally present in the human dental plaque. However,...

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

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.

Fusobacterium nucleatum - Friend or foe?

Fusobacterium nucleatum (F. nucleatum) is one of the most abundant Gram-negative anaerobic bacteria, part of the gut, and oral commensal flora, generally found in human dental plaque. Its presence could be associated with various human diseases, including, e.g., periodontal, angina, lung and gynecological abscesses. This bacteria can enter the blood circulation as a result of periodontal infection. It was proven that F. nucleatum migrates from its primary site of colonization in the oral cavity to other parts of the body. It could cause numerous diseases, including cancers. On the other hand, it was shown that Fusobacterium produces significant amounts of butyric acid, which is a great source of energy for colonocytes (anti-inflammatory cells). Therefore, it is very interesting to get to know the two faces of F. nucleatum.