Non-strict strand orientation of the Ca2+-induced dimerization of a conantokin peptide variant with sequence-shifted gamma-carboxyglutamate residues.
We have previously found a new mode of metal ion-induced helix-helix assembly for the gamma-carboxyglutamate (Gla)-containing, neuroactive conantokin (con) peptides that is independent of the hydrophobic effect. In these unique "metallo-zipper" assemblies of con-G and con-T[K7gamma], interhelical Ca(2+) coordination induces dimer formation with strictly antiparallel chain orientation in conantokin peptides in which Gla residues are positioned at "i, i+4, i+7, i+11" intervals. In order to probe the property of self-assembly in conantokin peptides with an extended Gla network, a con-T variant (con-T-tri) was synthesized that contains five Gla residues spaced at "i, i+4, i+7, i+11, i+14" intervals. Sedimentation equilibrium analyses showed that Ca(2+), but not Mg(2+), was capable of promoting con-T-tri self-assembly. Oxidation and rearrangement assays with Cys-containing con-T-tri variants revealed that the peptide strands in the complex can orient in both parallel and antiparallel forms. Stable parallel and antiparallel dimeric forms of con-T-tri were modeled using disulfide-linked peptides and the biological viability of these species was confirmed by electrophysiology. These findings suggest that small changes within the helix-helix interface of the conantokins can be exploited to achieve desired modes of strand alignment.
Dai
Qiuyun
Q
Beijing Institute of Biotechnology, Beijing, China. qy_dai@yahoo.com.cn
Xiao
Cai
C
Dong
Mingxin
M
Liu
Zhuguo
Z
Sheng
Zhenyu
Z
Castellino
Francis J
FJ
Prorok
Mary
M
D015055:1-Carboxyglutamic Acid / Q000737:chemistry*; D000595:Amino Acid Sequence; D002118:Calcium / Q000378:metabolism*; D002151:Calorimetry; D002942:Circular Dichroism; D019281:Dimerization; D008969:Molecular Sequence Data; D008978:Mollusk Venoms / Q000737:chemistry*; D018408:Patch-Clamp Techniques; D010456:Peptides, Cyclic / Q000737:chemistry* / Q000494:pharmacology; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects; D017386:Sequence Homology, Amino Acid; D014461:Ultracentrifugation
D008978:Mollusk Venoms; D010456:Peptides, Cyclic; D016194:Receptors, N-Methyl-D-Aspartate; D015055:1-Carboxyglutamic Acid; D002118:Calcium