Two-Metal Ion, Ni(II) and Cu(II), Binding α-Helical Coiled Coil Peptide

Abstract

Metalloproteins are an attractive target for de novo design. Usually, natural proteins incorporate two or more (hetero- or homo-) metal ions into their frameworks to perform their functions, but the design of multiple metal-binding sites is usually difficult to achieve. Here, we undertook the de novo engineering of heterometal-binding sites, Ni(II) and Cu(II), into a designed coiled coil structure based on an isoleucine zipper (IZ) peptide. Previously, we described two peptides, IZ-3adH and IZ-3aH. The former has two His residues and forms a triple-stranded coiled coil after binding Ni(II), Zn(II), or Cu(II). The latter has one His residue, which allowed binding with Cu(II) and Zn(II), but not with Ni(II). On the basis of these properties, we newly designed IZ(5)-2a3adH as a heterometal-binding peptide. This peptide can bind Cu(II) and Ni(II) simultaneously in the hydrophobic core of the triple-stranded coiled coil. The first metal ion binding induced the folding of the peptide into the triple-stranded coiled coil, thereby promoting the second metal ion binding. This is the first example of a peptide that can bind two different metal ions. This construction should provide valuable insights for the de novo design of metalloproteins.

Metal-binding properties and structural characterization of a self-assembled coiled coil: Formation of a polynuclear Cd–thiolate cluster

“…This is the first case of the adamantoid cage reported for a Cd 2+ complex with peptide ligands. The observed metal-thiolate cage in the AQ-C16C19 coiled coil is thus highly reminiscent of those similar inorganic adamantoid complexes of cadmium with monodentate thiolate ligands, [Cd 4 (SPh) 10 )] 2 − , [73] and a bicyclo(3.3.1)-nonane-like Cd 4 (S thiolate ) 11 metal center found in metallothioneins [55]. The Cd 2 + metal center in the AQ-C16C19 coiled coil is, however, structurally distinctive from the latter, especially in the way that its terminal ligands are carboxylic groups which are not observed to coordinate similar metal centers in metallothioneins.…”

“…An area of particular interest has been the introduction of metal-binding sites into the hydrophobic interiors of α-helical bundles and coiled coils. Examples of single metal ions that can be incorporated into coiled coils and helical bundles include heme centers [4] and mononuclear complexes of Zn 2+ [5][6][7][8], Cu 2+ [6,9,10], Cu + [11], Ni 2+ [10], Cd 2+ [12][13][14][15][16][17][18][19][20], Hg 2+ [12,14,16,17,[20][21][22][23][24][25][26], As 3+ [17,20,[26][27][28], Pb 2+ [18,20,29], and Bi 3+ [18]. Given these notable successes, the introduction of multinuclear metal complexes into synthetic proteins presents another challenging target to pursue.…”

Designing a functional type 2 copper center that has nitrite reductase activity within α-helical coiled coils

“…Examples of Cu(I) (13,14) and Cu(II) de novo designed helix bundles have been reported (15)(16)(17)(18)(19)(20)(21)(22)(23)(24). However, only a few examples of controlled binding of copper at (His) 3 sites are known (17,20,21).…”

“…However, only a few examples of controlled binding of copper at (His) 3 sites are known (17,20,21). Although Cu(I)/(II) redox processes were presented for a few systems (13,14,22), none was fully characterized in both oxidation states, which is essential for catalytic copper redox protein designs.…”

Engineering responsive mechanisms to control the assembly of peptide-based nanostructures

“…Numerous peptide models have been examined to define and potentially replicate the native functional roles of metal ions within defined polypeptide structural contexts [40][41][42][43][44][45]. One of the most striking observations to emerge from these studies is the ability of metal ions to induce conformational transitions from the unfolded to folded state [46][47][48][49][50][51][52] or between different folded states [53][54][55] through interaction with the side chains of appropriately placed amino acid ligands within the polypeptide backbone. Moreover, metal ions can influence the supramolecular assembly of diseaserelated protein fibrils [56,57], either enhancing or inhibiting the process, depending on the stereoelectronic properties of the specific metal.…”