This study presents purification, activity characterization, and 1 H NMR study of the novel antifungal peptide EcAMP1 from kernels of barnyard grass Echinochloa crus-galli. The peptide adopts a disulfide-stabilized ␣-helical hairpin structure in aqueous solution and thus represents a novel fold among naturally occurring antimicrobial peptides. Micromolar concentrations of EcAMP1 were shown to inhibit growth of several fungal phytopathogens. Confocal microscopy revealed intensive EcAMP1 binding to the surface of fungal conidia followed by internalization and accumulation in the cytoplasm without disturbance of membrane integrity. Close spatial structure similarity between EcAMP1, the trypsin inhibitor VhTI from seeds of Veronica hederifolia, and some scorpion and cone snail toxins suggests natural elaboration of different functions on a common fold.Antimicrobial peptides (AMPs) 4 are a structurally diverse group of generally small, positively charged peptides produced by various living organisms and demonstrating a wide spectrum of antimicrobial activity (1, 2). Natural sources of AMPs range from prokaryotes to higher animals, and their targets include bacteria, fungi, protozoa, and viruses. The mechanism of action of most known AMPs involves their direct or receptor-mediated interaction with microbial membranes (3-5). It has been generally accepted that membrane-disruptive AMPs kill microorganisms by provoking in different ways an increase in plasma membrane permeability. Non-membrane-disruptive peptides have been shown to target cell wall formation or traverse membranes and affect various internal cellular processes, for example, RNA, DNA, and/or protein biosynthesis. Some AMPs can combine disruptive and non-disruptive mechanisms of action (6). Moreover, mechanisms of action of the same peptide may differ depending on the target. Recent studies have also indicated that AMPs are multifunctional molecules; they can interact with host membrane receptors and influence diverse intracellular processes modulating the immune response of the host organism (7,8).Essential variety in detailed mechanisms of action and multifunctionality imply structural diversity among AMPs. The following structural groups are usually recognized: (i) linear peptides that form ␣-helices in contact with membranes; (ii) disulfide-containing with predominance of ␤-structural elements; and (iii) linear non-␣-helix-forming, usually with a high content of certain amino acid residues (1, 2, 9). Most of the approximately 200 AMP spatial structures known at present (see the Antimicrobial Peptide Database v2.26 (10)) fall into one of the first two groups. Further classification is based on unique features in the sequences and/or structures of AMPs. For example, thionins, defensins, nonspecific lipid transfer proteins, and hevein-and knottin-like peptides have been identified in plants (11-13).To characterize the array of AMPs produced by a plant under certain physiological conditions, we have carried out a systematic analysis of these peptides from...

No abstract

The yellow fluorescent protein (zFP538) from coral Zoanthus sp. belongs to a family of green fluorescent protein (GFP). Absorption and emission spectra of zFP538 show an intermediate bathochromic shift as compared with a number of recently cloned GFP-like red fluorescent and nonfluorescent chromoproteins of the DsRed subfamily. Here we report that the zFP538 chromophore is very close, if not identical, in chemical structure to that of DsRed. To gain insight into the mechanism of zFP538 fluorescence and chromophore structure and chemistry, we studied three chromophore-containing peptides isolated from enzymatic digests of zFP538. Like GFP and DsRed chromophores, these contain a p-hydroxybenzylideneimidazolinone moiety formed by Lys-66, Tyr-67, and Gly-68 of zFP538. One of the peptides studied, the hexapeptide FKYGDR derivative, is a proteolysis product of the zFP538 full-length polypeptide containing a GFP-type chromophore already formed and arrested at an earlier stage of maturation. The two other peptides are the derivatives of the pentapeptide KYGDR resulted from the protein in which the chromophore maturation process had been completed. One of these has an oxogroup at Lys-66 C(alpha) and is a hydrolysis product of another one, with the imino group at Lys-66 C(alpha). The N-unsubstituted imino moiety of the latter is generated by spontaneous polypeptide chain fragmentation at a very unexpected site, the former peptide bond between Phe-65 C' and Lys-66 N(alpha). Also observed in the entire protein under mild denaturing conditions, this fragmentation is likely the feature of native zFP538 chromophore that distinguishes it chemically from the DsRed chromophore.

No abstract

Spatial structure of the membrane channel-forming hexadecapeptide, zervamicin IIB, was studied by NMR spectroscopy in mixed solvents of different polarity ranging from CDCl 3 /CD 3 OH (9:1, v/v) to CD 3 OH/H 2 O (1:1, v/v). The results show that in all solvents used the peptide has a very similar structure that is a bent amphiphilic helix with a mean backbone root mean square deviation (rmsd) value of ca. 0.3 A î . Side chains of Trp 1 , Ile 2 , Gln 3 , Ile 5 and Thr 6 are mobile. The results are discussed in relation to the validity of the obtained structure to serve as a building block of zervamicin IIB ion channels.z 2000 Federation of European Biochemical Societies.