structure-coordination-determination-peptide-metal-complexes-using-1d

Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D <sup>1</sup>H NMR

Copper (I) binding by metallochaperone transport proteins prevents copper oxidation and release of the toxic ions that may participate in harmful redox ...

The Hebrew University of Jerusalem

The first NMR structure of a Cu(I)-bound metallochaperone model with the conserved sequence MT/HCXXC revealed that at pH ∼3.0 and ∼6.8 Cu(I) binds through one Cys and the Met rather than the two Cys residues, differently than at pH ∼8.5. This suggests a possible role of Met in metal transport.

NMR characterization of a Cu(I)-bound peptide model of copper metallochaperones: insights on the role of methionine.

Transition metal ions can be both beneficial and harmful to biological systems if not carefully regulated. A family of proteins that include a conserved sequence in their binding site of MXCXXC is responsible for delivery and homeostasis of different metals. Model studies present an effective tool for studying the parameters governing metal affinity, selectivity and other mechanistic aspects. Small-molecule, peptide-based, and advanced models will be presented, as well as functional models of potential industrial applications.

The MXCXXC class of metallochaperone proteins: model studies.

The first NMR structures of Cu(I) and Zn(II) peptide complexes as models of metallochaperones were derived with no predetermined binding mode. The cyclic peptide MDCSGCSRPG was reacted with Cu(I) and Zn(II) at low and moderate pH. This peptide features the conserved sequence of copper chaperones but with Asp at position 2 as appears in the zinc binding domain of ZntA. The structures were compared with those of the Cu(I) complexes of the wild-type sequence peptide MTCSGCSRPG. All analyses were conducted first with no metal-binding constraints to ensure accurate binding ligand assignment. Several structures included metal-Met binding, raising a possible role of Met in the metal transport mechanism. Both Cu(I) and Zn(II) gave different complexes when reacted with the peptide of the native-like sequence under different pH conditions, raising the possibility of pH-dependent transport mechanisms. Cu(I) bound the MTCSGCSRPG peptide through one Cys and the Met under acidic conditions and differently under basic conditions; Zn(II) bound the MDCSGCSRPG peptide through two Cys and the Met residues under acidic conditions and through one Cys and the Met under basic conditions, while Cu(I) bound the non-native Asp mutant peptide through the Asp and one Cys under both conditions, suggesting that Asp may inhibit pH-dependent binding for Cu(I). NOESY and ESI-HRMS supported the presence of an aqua ligand for Zn(II), which likely deprotonated under basic conditions to give a hydroxo group. Coordination similarities were detected among the model system and native proteins, which overall suggest that coordination flexibility is required for the function of metallochaperones.

Article	Year
NMR characterization of a Cu(I)-bound peptide model of copper metallochaperones: insights on the role of methionine. Chemical communications (Cambridge, England)\| PubMed ID: 21552638	2011
The MXCXXC class of metallochaperone proteins: model studies. Chemical Society reviews\| PubMed ID: 21695339	2011
Peptide models of Cu(I) and Zn(II) metallochaperones: the effect of pH on coordination and mechanistic implications. Inorganic chemistry\| PubMed ID: 23458158	2013

Michal S. Shoshan

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