Engineering of the hydrophobic core of an α-helical coiled coil

A New Mechanism for Metal Ion-assisted Interchain Helix Assembly in a Naturally Occurring Peptide Mediated by Optimally Spaced γ-Carboxyglutamic Acid Residues

“…With each incremental pH increase, an increasing amount of con-G association occurs, suggesting that the formation of the higher order species relies on the ionization of one or more acidic side-chains (Glu2 and/or Gla residues 3,4,7,10,14). Interestingly, neither con-T (GEg gY 5 QKMLg 10 NLRgA 15 EVKKN 20 A-NH 2 ) 21 nor con-R [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] (GEggV 5 AKMAA 10 gLARg 15 NI-NH 2 ), display Ca 2þ -mediated increases in M app , despite having Ca 2þ -induced secondary structural tendencies and biological activities similar to those of con-G. 18,22 A salient primary sequence difference between these latter peptides and con-G centers on the nature of the residue at position 7, which is Lys in con-T and con-R [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17], and Gla in con-G. The contribution of Gla7 to the associative properties of con-G was assessed through sedimentation equilibrium of con-G[g7K] in the presence and absence of Ca 2þ ( Table 1).…”

“…Hence, an i; i þ 4; i þ 7; i þ 11 arrangement of Gla residues appears to be important for supporting the self-association properties of con-G. The lack of metal ion-induced aggregation for con-T and con-R [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17], both of which contain a Lys at position 7, also argues for the importance of the aforementioned distribution of Gla residues in maintaining Ca 2þ -bridged interstrand contacts.…”

De Novo Designed Copper α‐Helical Peptides: From Design to Function

“…This apo-construct resulted in a fully folded homotrimeric α-helical coiled coil that bears a (His) 3 site at the C terminus available for copper binding. [76,102] The EPR spectrum of the [Cu II ](IZ-3aH) 3 adduct is typical of a Cu II Type 2 site and is consistent with an (N 3 O) donor set with a tetrahedral coordination geometry (Figure 6a). The UV/Vis spectrum of the Cu II -(peptide) 3 adduct presents a ligand-field band centered at 495 nm (ε = 300 m -1 cm -1 ) and the EPR features are typical of a Cu T2 site (A ʈ = 173 ϫ 10 -4 cm -1 ).…”

“…[18,99] It is therefore not surprising that in the field of de novo designed metallopeptides considerable effort has been directed in recent years towards the design and mimicking of functional metal (e.g., catalytic or electron transfer) sites in metalloenzymes. [25,26,28,29,76,102] Interestingly, metals such as mercury are not known to have a structural role in molecular biology. [3,5,10,16,59,77,100,101] The design of metal sites proceeds first with the control of the nature of the donor atoms.…”

“…[147] The construct was assembled by using a 19-mer peptide sequence (bpy-GELAQKLEQALQKLAAAHY-NH 2 ), which contains a 2,2Ј-bipyridyl (bpy) moiety linked at the N terminus and a His residue at the C terminus. [75,76,102,[149][150][151] However, they fold in the presence of metal ions as the coordination to the His residues compensates the destabilization of the construct due to the mutation of the Ile residues. This apo-construct resulted in a fully folded homotrimeric α-helical coiled coil that bears a (His) 3 site at the C terminus available for copper binding.…”