The solution structure of [Ala4]-desdimethylchlamydocin: a 1H n.m.r. relaxation study

Abstract

Many fungal peptides exhibit plant toxicity in a host-specific manner. Here we report a proton relaxation and two dimensional (2D) n.m.r. study of the [Ala⁴]-desdimethyl analogue of the fungal tetrapeptide chlamydocin. Interproton distances calculated from n.m.r. parameters agreed substantially with the corresponding distances in the crystalline form of dihydrochlamydocin. A solution conformational analysis was performed based on n.m.r. distance measurements and φ, ψ, and ω angles of the four residues plus χ_i rotamer populations. These data support the use of proton relaxation parameters as a basis for accurate solution conformational analysis. As a corollary, the data can also indicate within experimental error that the crystal and solution conformations of chlamydocin and the [Ala⁴]-desdimethyl analogue, respectively, are identical.