Comparison of cyanopeptolin genes in Planktothrix, Microcystis, and Anabaena strains: evidence for independent evolution within each genus

The major cyclic peptide cyanopeptolin 1138, produced by Planktothrix strain NIVA CYA 116, was characterized and shown to be structurally very close to the earlier-characterized oscillapeptin E. A cyanopeptolin gene cluster likely to encode the corresponding peptide synthetase was sequenced from the same strain. The 30-kb oci gene cluster contains two novel domains previously not detected in nonribosomal peptide synthetase gene clusters (a putative glyceric acid-activating domain and a sulfotransferase domain), in addition to seven nonribosomal peptide synthetase modules. Unlike in two previously described cyanopeptolin gene clusters from Anabaena and Microcystis, a halogenase gene is not present. The three cyanopeptolin gene clusters show similar gene and domain arrangements, while the binding pocket signatures deduced from the adenylation domain sequences and the additional tailoring domains vary. This suggests loss and gain of tailoring domains within each genus, after the diversification of the three clades, as major events leading to the present diversity. The ABC transporter genes associated with the cyanopeptolin gene clusters form a monophyletic clade and accordingly are likely to have evolved as part of the functional unit. Phylogenetic analyses of adenylation and condensation domains, including domains from cyanopeptolins and microcystins, show a closer similarity between the Planktothrix and Microcystis cyanopeptolin domains than between these and the Anabaena domain. No clear evidence of recombination between cyanopeptolins and microcystins could be detected. There were no strong indications of horizontal gene transfer of cyanopeptolin gene sequences across the three genera, supporting independent evolution within each genus.     

Comparison of Cyanopeptolin Genes in Planktothrix, Microcystis, and Anabaena Strains: Evidence for Independent Evolution within Each Genus

The major cyclic peptide cyanopeptolin 1138, produced by Planktothrix strain NIVA CYA 116, was characterized and shown to be structurally very close to the earlier-characterized oscillapeptin E. A cyanopeptolin gene cluster likely to encode the corresponding peptide synthetase was sequenced from the same strain. The 30-kb oci gene cluster contains two novel domains previously not detected in nonribosomal peptide synthetase gene clusters (a putative glyceric acid-activating domain and a sulfotransferase domain), in addition to seven nonribosomal peptide synthetase modules. Unlike in two previously described cyanopeptolin gene clusters from Anabaena and Microcystis, a halogenase gene is not present. The three cyanopeptolin gene clusters show similar gene and domain arrangements, while the binding pocket signatures deduced from the adenylation domain sequences and the additional tailoring domains vary. This suggests loss and gain of tailoring domains within each genus, after the diversification of the three clades, as major events leading to the present diversity. The ABC transporter genes associated with the cyanopeptolin gene clusters form a monophyletic clade and accordingly are likely to have evolved as part of the functional unit. Phylogenetic analyses of adenylation and condensation domains, including domains from cyanopeptolins and microcystins, show a closer similarity between the Planktothrix and Microcystis cyanopeptolin domains than between these and the Anabaena domain. No clear evidence of recombination between cyanopeptolins and microcystins could be detected. There were no strong indications of horizontal gene transfer of cyanopeptolin gene sequences across the three genera, supporting independent evolution within each genus.     

Human anti-porcine T cell response: blocking with anti-class I antibody leads to hyporesponsiveness and a switch in cytokine production.

Intervention in the molecular interactions that lead to an immune response is possible at various stages of Ag recognition and T cell activation. Perturbation of the interaction of the TCR with the MHC/peptide ligand complex is one approach that has shown promise for autoimmunity and graft rejection in blocking T cell-activated responses. In this study, we investigated the effect of altering the target MHC class I molecule by blocking with Abs. We established a system that analyzed the human T cell response against MHC class I+/class II- porcine stimulatory cell targets. The primary human response against porcine smooth muscle cells was CD8+ T cell dependent. In the presence of F(ab')2 fragments of the MHC class I-reactive Ab, PT-85, the proliferative response was inhibited and production of IL-2 and IFN-gamma was blocked. Moreover, in a secondary response, proliferation was reduced and type 1 cytokine levels were inhibited. In contrast, levels of IL-10 and IL-4 were sustained or slightly increased. These findings indicate that Ab against MHC class I blocked the recognition of porcine cells by the human CD8+ T cells and altered the cytokine secretion profile. Thus, a single treatment with PT-85 F(ab')2 directed against the MHC class I molecule provides an attractive approach to the induction of T cell tolerance that may provide long-term graft survival in porcine-to-human cell transplantation.     

Evidence for positive selection acting on microcystin synthetase adenylation domains in three cyanobacterial genera

Background  

Cyanobacteria produce a wealth of secondary metabolites, including the group of small cyclic heptapeptide hepatotoxins that constitutes the microcystin family. The enzyme complex that directs the biosynthesis of microcystin is encoded in a single large gene cluster (mcy). mcy genes have a widespread distribution among cyanobacteria and are likely to have an ancient origin. The notable diversity within some of the Mcy modules is generated through various recombination events including horizontal gene transfer.     

Changes in tissue protein levels as a result of endurance exercise

We previously reported that endurance training increases amino acid catabolism. In this study, the effects of an acute endurance exercise bout on tissue protein levels and urea excretion have been investigated. Exhaustive exercising of trained rats resulted in an increase in ammonia excretion but there was no significant change in urea excretion. Protein levels of muscle and liver were significantly decreased by an exhaustive bout of exercise. In muscle, both the soluble and myofibrillar protein fractions were decreased in exhausted rats. These results demonstrate that during exercise there is a net loss of protein in muscle and liver.