Plicatamide (Phe-Phe-His-Leu-His-Phe-His-dc⌬DOPA), where dc⌬DOPA represents decarboxy-(E)-␣,␤-dehydro-3,4-dihydroxyphenylalanine, is a potently antimicrobial octapeptide from the blood cells of the solitary tunicate, Styela plicata. Wild type and methicillin-resistant Staphylococcus aureus (MRSA) responded to plicatamide exposure with a massive potassium efflux that began within seconds. Soon thereafter, treated bacteria largely ceased consuming oxygen, and most became nonviable. Native plicatamide also formed cation-selective channels in model lipid bilayers composed of bacterial lipids. Methicillin-resistant S. aureus treated with plicatamide for 5 min contained prominent mesosomes as well as multiple, small dome-shaped surface protrusions that suggested the involvement of osmotic forces in its antimicrobial effects. To ascertain the contribution of the C-terminal dc⌬DOPA residue to antimicrobial activity, we synthesized several analogues of plicatamide that lacked it. One of these peptides, PL-101 (Phe-Phe-His-Leu-His-Phe-HisTyr-amide), closely resembled native plicatamide in its antimicrobial activity and its ability to induce potassium efflux. Plicatamide was potently hemolytic for human red blood cells but did not lyse ovine erythrocytes. The small size, rapid action, and potent anti-staphylococcal activity of plicatamide and PL-101 make them intriguing subjects for future antimicrobial peptide design.Phe-Phe-His-Leu-His-Phe-His-dc⌬DOPA (plicatamide) 1 is a modified octapeptide found in the hemocytes of Styela plicata (1). In the preceding sequence, dc⌬DOPA indicates decarboxy-(E)-␣,␤-dehydro-3,4-dihydroxyphenylalanine. Although the sequence of plicatamide did not resemble a conventional antimicrobial peptide, we examined its antimicrobial properties because hemocytes are key participants in innate antimicrobial defenses. Despite its small size, plicatamide proved to be a potent, rapidly acting, and broad spectrum antimicrobial. We also prepared the following four synthetic analogues that differed from plicatamide only in their C-terminal residue: tyrosine amide in PL-101; tyrosine acid in PL-102; DOPA (3,4-dihydroxyphenylalanine) acid in PL-103; and DOPA-amide in PL-104. Of these octapeptides, PL-101 most closely simulated the antimicrobial properties of native plicatamide. This report will describe the effects of plicatamide on staphylococci. MATERIALS AND METHODS Peptide PurificationNative plicatamide was purified from freshly harvested hemocytes (blood cells) of S. plicata as described recently (1). We determined their peptide content either by performing quantitative amino acid analysis or by doing analytical reverse phase-HPLC on a C18 column and then computing and comparing the area under the curve (AUC) at 215 nm with the AUC of an appropriate standard previously subjected to quantitative amino acid analysis. Peptide SynthesisThe synthetic peptides used in our initial experiments were customsynthesized by Fmoc (N-(9-fluorenyl)methoxycarbonyl) chemistry at Research Genetics (Huntsville, AL) and puri...

Initiation and refinement of expression of the Ind homeodomain protein in the Drosophila embryo is coordinately regulated by global dorsoventral patterning pathways Dorsal, Egfr, and Dpp, and well as by Vnd, which positions the ventral boundary of Ind. Therefore, we set out to look for novel regulators of dorsoventral patterning by screening the Exelixis deficiency collection for modified expression of Ind. Indeed, we found deficiencies that remove components of the known signaling pathways had altered or lost ind expression. These findings included deficiencies that remove screw, dpp, and egfr as well as deficiencies that remove ind itself. In addition, we found several deficiencies that had altered or loss of ind expression. We also observed phenotypes suggestive of dorsoventral patterning defects such as twisting during gastrulation, and defects associated with loss of dorsal specification. These include a pair of overlapping deficiencies that produced ventralized embryos. We find that transheterozygotes of these two deficiencies are also ventralized. There are seven genes common to both deficiencies, including CG11582, which encodes a twisted gastrulation-like protein. These two deficiencies are also allelic with shrew mutations. Here, we present data supporting the conclusion that CG11582 is the gene affected in shrew mutants. Developmental Dynamics 236:3524 -3531, 2007.

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Agar has been shown to interfere with the activity of some antibiotics against Staphylococcus aureus. This interference has been observed as an increase in the minimal inhibitory concentration and in the diameter of the zone of inhibition. Purifying the agar with water extractions substantially reduced this adverse effect.