Uncapping the N-terminus of a ubiquitous His-tag peptide enhances its Cu²⁺ binding affinity

Abstract

Copper(ii) complexes with the studied His-rich motif are polymorphic, exhibit a 3–10 helix, and are more stable than a His6-tag complex.

Histidine-Rich C-Terminal Tail of Mycobacterial GroEL1 and Its Copper Complex─The Impact of Point Mutations

“…S5A,B). 22,27,28 This finding is supported by the presence of the d−d band at 500 and 620 nm (negative and positive Cotton effect), corresponding to the copper(II)−amide nitrogen interactions in peptide complexes (Figure S5C). 4+ , with a maximum concentration at around pH 4.0, most probably come from the deprotonation of a His and Glu residue, respectively.…”

“…22,27 EPR parameters for the complex at pH 5.11 (A = 177.1 G, g ∥ = 2.27, Figure S6B) also support the interaction of Cu(II) with two nitrogen atoms. 22 A {2N im } coordination mode is therefore assigned to the [CuH 6 L] 3+ and [CuH 5 L] 2+ species. [CuH 4 L] + , with a maximum concentration at pH 6.0, could arise from the deprotonation of a fourth His residue.…”

“…22,27 EPR parameters for the complex at pH 5.07 (A = 176.5 G, g ∥ = 2.27, Figure S5B) confirm the interaction of Cu(II) with two nitrogen atoms. 22 The other four species, [CuH probably, non-metal-binding His residues. pK a values of 4.75, 5.47, 6.16, and 6.81 for these steps could probably correspond to pK a = 5.44, 6.06, 6.42, and 7.28, respectively, for His residues in the free ligand.…”

“…The final UV−vis (λ max = 525 nm) and EPR (A = 196.9, g ∥ = 2.19) set of parameters at pH 11.04 (λ max = 530 nm) strongly confirms the interaction of Cu(II) with four nitrogen atoms (Figure S6A,B). 22,27,33 The coordination modes of [CuHL] 2C). [CuH 6 L] 3+ with a maximum concentration at pH 4.5 most probably comes from the deprotonation of the first His side chain.…”

Cationic Peptides and Their Cu(II) and Ni(II) Complexes: Coordination and Biological Characteristics

“…They were similar to those characteristic (N π ) in the imidazole ring where the average log K His is 6.6 [ 31 ]. However, in many models of peptide ligands, lower values were reported [ 37 , 38 , 39 , 40 , 41 ]. A second (N τ ) imidazole nitrogen remains protonated and, usually, proton dissociation occurs, here, at high pH and log K = 14 [ 42 ].…”