Non-strict strand orientation of the Ca2+-induced dimerization of a conantokin peptide variant with sequence-shifted γ-carboxyglutamate residues

• Published in: Peptides (New York, N.Y. : 1980) N.Y. : 1980), 2009-05, Vol.30 (5), p.866-872
• Main Authors: QIUYUN DAI, CAI XIAO, MINGXIN DONG, ZHUGUO LIU, ZHENYU SHENG, CASTELLINO, Francis J, PROROK, Mary
• Format: Article
• Language: English
• Subjects: 1-Carboxyglutamic Acid - chemistry; Amino Acid Sequence; Biological and medical sciences; Calcium - metabolism; Calorimetry; Circular Dichroism; Dimerization; Fundamental and applied biological sciences. Psychology; Molecular Sequence Data; Mollusk Venoms - chemistry; Patch-Clamp Techniques; Peptides, Cyclic - chemistry; Peptides, Cyclic - pharmacology; Receptors, N-Methyl-D-Aspartate - drug effects; Sequence Homology, Amino Acid; Ultracentrifugation; Vertebrates: endocrinology
• ISSN: 0196-9781; 1873-5169
• DOI: 10.1016/j.peptides.2009.01.010

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.