Identification of the Flavobacterium johnsoniae cysteate-fatty acyl transferase required for capnine synthesis and for efficient gliding motility.

Sulfonolipids (SLs) are bacterial lipids that are structurally related to sphingolipids. Synthesis of this group of lipids seems to be mainly restricted to Flavobacterium, Cytophaga and other members of the phylum Bacteroidetes. These lipids have a wide range of biological activities: they can induce multicellularity in choanoflagellates, act as von Willebrand factor receptor antagonists, inhibit DNA polymerase, or function as tumour suppressing agents. In Flavobacterium johnsoniae, their presence seems to be required for efficient gliding motility. Until now, no genes/enzymes involved in SL synthesis have been identified, which has been limiting for the study of some of the biological effects these lipids have. Here, we describe the identification of the cysteate-fatty acyl transferase Fjoh_2419 required for synthesis of the SL precursor capnine in F. johnsoniae. This enzyme belongs to the α-oxoamine synthase family similar to serine palmitoyl transferases, 2-amino-3-oxobutyrate coenzyme A ligase and 8-amino-7-oxononanoate synthases. Expression of the gene fjoh_2419 in Escherichia coli caused the formation of a capnine-derived molecule. Flavobacterium johnsoniae mutants deficient in fjoh_2419 lacked SLs and were more sensitive to many antibiotics. Mutant growth was not affected in liquid medium but the cells exhibited defects in gliding motility.

Akt1 intramitochondrial cycling is a crucial step in the redox modulation of cell cycle progression.

Akt is a serine/threonine kinase involved in cell proliferation, apoptosis, and glucose metabolism. Akt is differentially activated by growth factors and oxidative stress by sequential phosphorylation of Ser(473) by mTORC2 and Thr(308) by PDK1. On these bases, we investigated the mechanistic connection of H(2)O(2) yield, mitochondrial activation of Akt1 and cell cycle progression in NIH/3T3 cell line with confocal microscopy, in vivo imaging, and directed mutagenesis. We demonstrate that modulation by H(2)O(2) entails the entrance of cytosolic P-Akt1 Ser(473) to mitochondria, where it is further phosphorylated at Thr(308) by constitutive PDK1. Phosphorylation of Thr(308) in mitochondria determines Akt1 passage to nuclei and triggers genomic post-translational mechanisms for cell proliferation. At high H(2)O(2), Akt1-PDK1 association is disrupted and P-Akt1 Ser(473) accumulates in mitochondria in detriment to nuclear translocation; accordingly, Akt1 T308A is retained in mitochondria. Low Akt1 activity increases cytochrome c release to cytosol leading to apoptosis. As assessed by mass spectra, differential H(2)O(2) effects on Akt1-PDK interaction depend on the selective oxidation of Cys(310) to sulfenic or cysteic acids. These results indicate that Akt1 intramitochondrial-cycling is central for redox modulation of cell fate.

Electrophoretic studies on the chelating tendency of bioactive sulphur-containing amino acids. The metal-methylcysteine-cysteine system.

Stability constants of binary Fe(III)-methylcysteine, Cr(III)-methylcysteine and mixed Fe(III)-methylcysteine-cysteine, Cr(III)-methylcysteine-cysteine complexes have been determined by paper electrophoresis at 0.1 M ionic strength and a temperature of 35 degrees C. The stability constants of Fe(III)-methylcysteine-cysteine and Cr(III)-methylcysteine-cysteine mixed complexes were found to be 6.00 +/- 0.07 and 5.05 +/- 0.15 (logarithm of stability constant values), respectively.