Phalloidine structure

The same mushrooms contain several fast-acting toxic heptapeptides, the phalloidins, whose structures are similar to those of the amanitins. However, they contain a reduced sulfur atom (—S—) in the cross-bridge. They are specifically toxic to the liver.c The same mushrooms also contain an antidote to the phalloidins, antamanide. This cyclic... 

The first total synthesis of a phallotoxin was that of norphalloin, the norvaline analogue of phalloidin.16 This synthesis, outlined in Scheme 2, initially involves the synthesis of two building blocks followed by their covalent binding via a tryptathionine moiety. Subsequent deprotection and coupling steps using classical methods of peptide synthesis results in the formation of norphalloin, which has proved to be even more toxic than the natural toxins. Since the synthesis of norphalloin, a number of synthetic analogues have been synthesized in order to obtain information on structure-activity relationships.[7 8]... 

The cytoskeleton is a cellular scaffold within the cytoplasm of the cell or within structures such as flagella, cilia, and lamellipodia. The cytoskeleton plays a crucial role in cellular integrity/structural support, cell division, cell motility, and intracellular transport. Staining of the cytoskeleton may be achieved by immunofluorescence in fixed cells however there are also dyes available, such as fluorescently labelled phalloidin, which directly labels actin filaments, as well as tubulin tracker which labels microtubules (Molecular Probes). Phalloidin is poorly permeable to living cells however, phalloidin derivatives with improved permeability properties are also available. Although both phalloidin derivatives and microtubule tracker can be used in live cells, it should be noted that both dyes are toxic as they inhibit cell division, and therefore limits their applications. 

A plausible hypothesis at this stage (about 1943) was that a sequence occurred tryptophan —> an intermediate kynurenine kynurenic acid. It was thought that the intermediate between tryptophan and kynurenine might be the so-called a-hydroxytryptophan (for structure see p. 83), which had been obtained (917) on hydrolysis of phalloidine, a toxic peptide from the fungus Amanita pkalloides (567) such a pathway received... 

On hydrolysis with acids phalloidin yields L-alanine, 4-cis-L-hydroxyproline, D-threonine, L-y, -dihydroxyleucine, L-cysteine and j8-oxindolalanine ( oxytryptophan ). The tryptophan derivative is not a genuine building component of the cyclic peptides it is formed by hydrolysis of a thioether crosslink between position 2 of tryptophan and the side chain of cysteine (tryptathionine). The structure of the bicyclic heptapeptide is shown in Fig. 21. 

Shortly after the structure elucidation of phalloidin in 1955 attempts at synthesis were started, but they led to success only in 1977 with the synthesis of phalloin by E. Munekata. Serious difficulties were caused by the y-hydroxyleucine residue, which during the operations of peptide syntheses readily forms a y-lactone yet this undesired side reaction cannot be prevented by the temporary blocking of the tertiary hydroxyl groups. 

Phallotoxins heterodetic, cyclic heptapeptides, present in Amanita phalloides. Together with the Amatoxins (see), P. are the main toxic components of this fungus. The chief P. are phalloidin, phalloin and phallacidin (Fig.). Phallacidin is similar to phalloidin, but the D-threonine-alanine grouping is replaced by valyl-D-erythro-P-hydroxyaspartic acid. P. are not as toxic as the amatoxins, but they act more quickly. The structural requirements for toxicity... 

The conformational features of ring-structure, hypercyclization, the presence of N-methyl amino acids and other imino acidsare not the attributes of peptide antibiotics only. The toxic principles of Amanita phalloides, phalloidin and amanitin exhibit similar characteristics and the more recently discovered and synthesized component of the same fungus antaminid (III), a peptide which can antagonize the toxic effects of amanitin, is also cyclic. In this particular case no D-amino... 

Sorm and Keil (535) recently studied the structure of phalloidin in a preparation whose homogeneity had been checked by partition chromatography on starch and by ionophoresis. The ultraviolet spectrum was identical to that determined by Wieland (628). The total hydrolysis of this phalloidin yielded only the following amino acids, identified by chromatography alanine, cysteine, allohydroxyproline, and hydroxy-tryptophan. An investigation of the various peptides obtained on partial hydrolysis led Sorm and Keil to propose for phalloidin, considered to be a... 

Phalloidin is one of the poisons of the mushroom Amanita phaUoides with great toxicity. Only 50 pg are lethal for a mouse. Seven different amino acids are involved in its structure including such unusual hydroxy amino acids as hydroxy-leucine and allothreonine (T. Wieland). There is a bridge between tryptophan and the SH group of cysteine which yields hydroxy tryptophan upon hydrolysis. The formula is not reproduced here. 

Figure 3. Focal adhesions in (A,B) embryonic fibroblasts and (C,D) tumor cells removed from MMTY-PyMT mice. Cells were plated on fibronectin in serum-free medium. Fibroblasts were stained with rhodamine-phalloidin, FITC conjugated anti-paxillin antibodies, and Hoechst 33258 stain. Tumor cells were stained with rhodamine-phalloidin and FITC conjugated anti-vinculin antibodies. Fluorescence images of the cells were obtained using a decovolution microscope. Paxillin and vinculin (green) are localized to ends of microfilaments (red) in focal adhesions. Mgat5 (A) fibroblasts and (C) tumor cell show focal adhesions but these structures are absent in MgatS (B) fibroblasts and (D) tumor cells. (E), T cell receptor dependent stimulation measured by H-thymi-dine incorporation in response to anti-CD3 antibodies at 48h (F) Model of responses to variable substratum adhesions for Mgat5 and Mgat5 cells.

Fixation without Methanol (Hand Devitellinization of Embryos). Often, the highest quality preparations are obtained by not exposing the embryos to methanol, which destroys membrane and other structures. In addition, some reagents such as fluores-cently labeled phalloidin will not work if the embryos have been exposed to methanol. Foregoing the methanol, however, necessitates removing the vitelline membrane by hand. We find this procedure to be most satisfactory (see Protocol 9.3, Method 5). For examples of embryos prepared by this method, see Figure 9.4B,C. 

Figure 4. Structure of a thiol-capturing phalloidin derivative.

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