Weak Acid-Base Interactions of Histidine and Cysteine Affect the Charge States, Tertiary Structure, and Zn(II)-Binding of Heptapeptides

Comparison of the pH‐dependent formation of His and Cys heptapeptide complexes of nickel(II), copper(II), and zinc(II) as determined by ion mobility‐mass spectrometry

“…The conformer is further supported by the increase in Ni(II) chelation at pH ≥ 8.0 which is likely related to the deprotonation of the Cys substituent groups (p K a ≈ 8.3) and results in the His 1 , Cys 2 , Cys 7 , and C‐terminus carboxylate coordination of Ni(II) (Figure ). This type of Ni(II) coordination is similar to the Zn(II) coordination previously found by our research, and the L‐J CCS measurement of the conformer in Figure and the IM‐MS measured CCS (Table ) are in agreement within their associated error bars.…”

“…Figure shows that the free [amb 5 ‐H] − was the main species at pH ≤ 7.0, for all amb 5A‐F species, and that A , B , and C formed the highest percentage of negative ion Ni(II) complexes over pH ≥ 8. Our previous study of A to F located low energy B3LYP/LanL2DZ conformers of [amb 5 ‐H] − that were stabilized by the Cys thiolate and C‐terminus carboxylate salt‐bridged or H‐bonded to the imidazolium or imidazole groups of His. These conformers were also in agreement with previous studies of the deprotonation of cysteine at the side chain rather than the amidated C‐terminus …”

“…The formation of negatively charged species from amb 5A‐F + Zn(II) over pH 4.5 to 10 has been recently published, and the results of the positively charged species from the equimolar amb 5A‐F + Zn(II) samples are shown in Figure S5. The relative percent of formation of the Zn(II) complexes from the negative and positive ion results are compared with those of Ni(II) and Cu(I)/(II) in Figure .…”

“…Recently, an ion mobility-mass spectrometry (IM-MS) study is conducted on how the primary structure of ac-His 1 -Cys 2 -Gly 3 -Pro 4 -Tyr 5 -His 6 -Cys 7 ( Figure 1A) and its modified counterparts (B-F) showed how the weak acid and base properties of the Cys and His in their primary structure affected their overall charge states, conformations, collision-induced dissociations, and Zn(II) chelation. 1,2 To extend this research, we have undertaken a pH-dependent study of the oligopeptides A to F to determine how their primary structure affects their chelation of nickel and copper ions and have compared them to our previous study of zinc. Our previous IM-MS studies of metal binding have shown behavior that is closely correlated to that of the solution phase, because the covalent interactions between the metal ion and peptide are robust enough to be conserved during electrospray ionization (ESI).…”

Collisional Dynamics Simulations Revealing Fragmentation Properties of Zn(II)-Bound Poly-Peptide

“…2 These functions are performed by incorporating zinc as a cofactor into proteins or peptides usually via thiolate groups of cysteine and the imidazole groups of histidine in a tetrahedral coordination geometry. 3 Ion mobility -mass spectrometry (IM-MS) [3][4][5] with molecular modelling and novel ion activation methods can be used to determine the accurate structure of these zinc containing metallopeptides. Previous studies of methanobactin 6,7 from Methylosinus trichosporium and analogue methanobactin (amb) peptides [3][4][5][8][9][10][11] show the IM-MS analyses in negative ion mode is particularly informative because it shows a distinct pH dependence for the metal binding and provides the protonation state of the acidic and basic binding sites, the charge of the metal ion, and the collision cross section of the conformer.…”