Zn-Enhanced Asp-Rich Antimicrobial Peptides: N-Terminal Coordination by Zn(II) and Cu(II), Which Distinguishes Cu(II) Binding to Different Peptides

Abstract

The antimicrobial activity of surfactant-associated anionic peptides (SAAPs), which are isolated from the ovine pulmonary surfactant and are selective against the ovine pathogen Mannheimia haemolytica, is strongly enhanced in the presence of Zn(II) ions. Both calorimetry and ITC measurements show that the unique Asp-only peptide SAAP3 (DDDDDDD) and its analogs SAAP2 (GDDDDDD) and SAAP6 (GADDDDD) have a similar micromolar affinity for Zn(II), which binds to the N-terminal amine and Asp carboxylates in a net entropically-driven process. All three peptides also bind Cu(II) with a net entropically-driven process but with higher affinity than they bind Zn(II) and coordination that involves the N-terminal amine and deprotonated amides as the pH increases. The parent SAAP3 binds Cu(II) with the highest affinity; however, as shown with potentiometry and absorption, CD and EPR spectroscopy, Asp residues in the first and/or second positions distinguish Cu(II) binding to SAAP3 and SAAP2 from their binding to SAAP6, decreasing the Cu(II) Lewis acidity and suppressing its square planar amide coordination by two pH units. We also show that these metal ions do not stabilize a membrane disrupting ability nor do they induce the antimicrobial activity of these peptides against a panel of human pathogens.

Antimicrobial peptides: mechanism of action, activity and clinical potential

“…They seem to utilize metal ions and the negatively charged components of the microbial membrane to form salt bridges, thus interacting with microbes [ 88 ], which are similar to the charge-neutralization characteristics of larger proenzyme [ 89 ]. For example, ovine pulmonary surfactant associated anion peptide (SAAP), the first discovered anionic AMP with 5–7 aspartate residues, had antimicrobial activity to the ovine pathogen Mannheimia haemolytica in the presence of Zn ions [ 90 ]. When 0.14 mol/L NaCl and EDTA were added into the surfactant solution, its bactericidal activity was largely inhibited, while restored when ZnCl 2 was replenished.…”

A DNA damage-induced phosphorylation circuit enhances Mec1ATR-Ddc2ATRIPrecruitment to Replication Protein A

“…Given that the crystallisation conditions contain ZnCl 2 , we postulate the metal ions to be Zn 2+ . Indeed, peptides that are aspartate-rich have been shown to bind to zinc ions (Miller et al, 2021), and in the structure, the ions are tetrahedrally coordinated by carboxyl groups of the aspartate side chains, oxygen groups of the phosphoserine, and water molecules ( Figure 3D ). The co-ordination geometry and bond lengths are consistent with zinc binding (∼2.0 Å in the structure) and were supported by using the CMM metal binding site validation server (Zheng et al, 2017).…”

The Synergy Between Zinc and Antimicrobial Peptides: An Insight into Unique Bioinorganic Interactions

“…Phosphate inhibits their bactericidal activity, while Ca(II) and Mg(II) were found to have no effect. Zn(II) is required in the antimicrobial activity against K. pneumoniae, E. coli, S. aureus, S. faecalis, Pasteurella haemolytica, and Mannheimia haemolytica [94,96]. Though, only P. haemolytica and Mannheimia had MIC values in the low micromolar range [94,96].…”

“…Zn(II) is required in the antimicrobial activity against K. pneumoniae, E. coli, S. aureus, S. faecalis, Pasteurella haemolytica, and Mannheimia haemolytica [94,96]. Though, only P. haemolytica and Mannheimia had MIC values in the low micromolar range [94,96]. The bioactivity of synthetic aspartic acid polymers was also tested, and it was observed that the MIC of these peptides was proportional to the number of Asp residues and that Zn(II) was still required for their bactericidal functionality [94].…”