Showing papers by "Guillaume Mitta published in 1999"
TL;DR: The isolation of two isoforms of a novel cysteine-rich peptide from haemocytes and plasma of the mussel, Mytilus galloprovincialis, suggests that myticins are synthesized as preproproteins and then processed by various proteolytic events before storage of the active peptide in the haemocyte.
Abstract: We report here the isolation of two isoforms of a novel cysteine-rich peptide from haemocytes (isoform A of 4.438 Da and B of 4.562 Da) and plasma (isoform A) of the mussel, Mytilus galloprovincialis. The two molecules display antibacterial activity against gram-positive bacteria, whereas only isoform B is active against the fungus Fusarium oxysporum and a gram-negative bacteria Escherichia coli D31. Complete peptide sequences were determined by a combination of Edman degradation, mass spectrometry and cDNA cloning using a haemocyte cDNA library. The mature molecules, named myticins, comprise 40 residues with four intramolecular disulfide bridges and a cysteine array in the primary structure different to that of the previously characterized cysteine-rich antimicrobial peptides. Sequence analysis of the cloned cDNAs revealed that myticin precursors consist of 96 amino acids with a putative signal peptide of 20 amino acids, the antimicrobial peptide sequence and a 36-residue C-terminal extension. This structure suggests that myticins are synthesized as preproproteins and then processed by various proteolytic events before storage of the active peptide in the haemocytes. Myticin precursors are expressed mainly in the haemocytes as revealed by Northern blot analysis.
227 citations
TL;DR: Immunocytochemistry at both the optical and ultrastructural levels showed that defensins are predominantly located in vesicles of a granulocyte subclass of hemocytes containing small granules, and that MGD immune reactivity existed in granular structures of enterocytes.
Abstract: MGD1 (Mytilus galloprovincialis defensin 1), a new member of the arthropod defensin family, is a 4 kDa antibacterial peptide previously isolated from the plasma of Mediterranean mussels. We report here the presence of MGD1 in the organelle-rich fraction of hemocytes and the cDNA sequence corresponding to MGD1 and one new isoform mRNA: MGD2. Sequence analysis indicated that MGDs are synthesised as precursors consisting of a putative signal peptide of 21 residues, the active peptide of 39 amino acids and a 21 residue carboxyl-terminal extension, rich in acidic amino acids. Localisation of the transcripts by northern blot revealed that the precursors are abundantly expressed in hemocytes. Immunocytochemistry at both the optical and ultrastructural levels showed that defensins (i) are predominantly located in vesicles of a granulocyte subclass of hemocytes containing small granules, (ii) are also found in large clear granules of another granulocyte subclass, and (iii) that MGD immune reactivity existed in granular structures of enterocytes. Finally, we revealed that bacterial challenge triggered a plasmatic increase of MGD1 concentration and gave evidence of the simultaneous release of the peptides from the hemocytes.
194 citations
TL;DR: Most second-generation ON antisense analogs do not activate RNase H, so alternative strategies to arrest translation in a reticulocyte cell-free assay programmed by VSV mRNAs have been explored.
Abstract: Most second-generation ON antisense analogs do not activate RNase H. Alternative strategies to arrest translation in a reticulocyte cell-free assay programmed by VSV mRNAs have been explored.