A copper complex formed with neurokinin B: binding stoichiometry, redox properties, self-assembly and cytotoxicity

Abstract

The tachykinin neuropeptide of neurokinin B (NKB) is a copper-binding amyloid peptide with important roles in the regulation of physiological functions and pathophysiological processes in the central and peripheral nervous...

Essential Role of Histidine for Rapid Copper(II)-Mediated Disassembly of Neurokinin B Amyloid

“…Furthermore, the lag phase for NKB(H 3 W) was longer than for NKB(H 3 F), which may reflect the larger size of Trp compared to Phe and the time required to arrange into pre-fibrillar oligomers that were large enough to allow ThT binding. Taken together with previous data showing that NKB(H 3 T) and NKB(H 3 A) mutants do not fibrillize [ 22 , 23 ], this experiment supports the idea that it is aromaticity at position 3 that is important for fibrillization, and not His specifically.…”

“…Previous studies have shown that the copper disassembly of NKB fibrils can be monitored using ThT fluorescence. Disassembly leads to a loss of ThT fluorescence, which has been corroborated by analysis using atomic force microscopy [ 23 ] and electron microscopy [ 22 ]. Firstly, the wildtype NKB was analyzed.…”

“…Previous studies have shown that mutation of His3 in NKB to either a Thr [ 22 ] or to an Ala [ 23 ] abolished amyloid formation. If fibrillization is only driven by the hydrophobic C-terminal region containing the diphenylalanine sequence, then mutation of the residue at the third position should have little effect.…”

“…NKB (sequence = DMHDFFVGLM-NH 2 ) can rapidly form an amyloid and contains a pair of Phe residues which have been proposed to support fibril formation via π-stacking interactions [ 22 ]. However, in NKB, the Phe residues themselves are not sufficient for fibril formation because mutation of histidine (His) at position 3 to either a threonine or an alanine eliminates amyloid assembly [ 22 , 23 ]. It is not clear how the His contributes to fibril formation given its range of possible noncovalent interactions, but it is most likely that histidine’s aromaticity and/or hydrogen bonding ability are key to fibril assembly [ 24 , 25 ].…”

Interactions of neurokinin B with copper(ii) ions and their potential biological consequences

“…In contrast, a standard 1 : 1 Cu(NKB) stoichiometry was proposed more recently on the basis of mass spectrometry experiments. 28 The latter result cannot be treated as definitive, however, because mass spectrometry of Cu(II)-peptide complexes is prone to a number of experimental issues which compromise the reliability of results. 29 In this study, we re-investigated the Cu(II) complexation by NKB using potentiometry, spectroscopic methods, and DFT calculations.…”