NMDA‐receptor antagonist requirements in conantokin‐G

FEBS Letters

Prorok, Mary¹  Blandl, Tamas¹  Castellino, Francis J¹ 

[1] Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 4655, USA

关键词: Conantokin-G;    N-Methyl-d-aspartate receptor;    Ion channel;    Polypeptide conformation;    Metal binding;    γ-Carboxyglutamate;   

DOI  :  10.1016/S0014-5793(98)01077-1

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

A series of variants of the neuroactive 17-residue γ-carboxyglutamate-(Gla)-containing polypeptide, conantokin-G (con-G), were synthesized with the intention of determining those features that were important for its N-methyl-d-aspartate (NMDA) receptor-targeted antagonist activity and for adoption of its divalent cation-dependent α-helical conformation. Employing the binding of [³H]dizolcipine (MK-801) as an assay for open receptor ion channels in rat brain membranes, which displays inhibition by con-G (IC₅₀=0.48 μM), it was found that replacement by an Ala residue of Gla⁴ led to complete inactivation of the peptide, whereas a similar replacement of Gla³ resulted in a 20-fold decreased potency. Ala substitutions for Gla¹⁰ and Gla¹⁴ did not substantially affect [³H]MK-801 binding. This same substitution at Gla⁷ appeared to slightly enhance binding. Ala replacements of non-Gla residues demonstrated that four of them, viz. Glu², Leu⁵, Gln⁹, and Ile¹², possessed at least 200-fold decreases in inhibitory potency, whereas similar replacements at Gly¹, Leu¹¹, and Arg¹³ resulted in peptides with 8- to 12-fold increases in the IC₅₀ values. The remaining amino acid residues tested in the single Ala replacement series showed no significant changes in the inhibitory characteristics of wild-type con-G. Additional studies with carboxyl-terminal truncated peptides revealed that the carboxyl-terminal 4 amino acids were unimportant for this activity. There was no strict correlation of inhibition of [³H]MK-801 binding with the ability of these peptides to form cation-dependent α-helices. Peptides with notably low α-helical content in the presence of these cations were lacking at least one, or both, of Gla¹⁰ and Gla¹⁴. Con-G[Gla^3,4,7,10,14E] and con-G[Gla^7,10,14E] were the only peptides that remained in a completely random conformation upon metal ion addition.

【 授权许可】

Unknown