The stable evolutionary fixation of a bifunctional tyrosine-pathway protein in enteric bacteria

Abstract The bifunctional T-protein (chorismate mutase-T: cyclohexadienyl dehydrogenase) of l -tyrosine biosynthesis was found to be present in all genera making up the enteric bacteria. The dehydrogenase component of the T-protein was active with both prephenate and l -arogenate, showing it to be a cyclohexadienyl dehydrogenase. The dehydrogenase component, but not the mutase component, of the T-protein was feedback-inhibited by l -tyrosine. Unlike some other bifunctional proteins, the T-protein has evolved recently and is not ubiquitous. However, once the biochemical specialization of bifunctionality becomes established, the results indicate that such character states are strongly conserved through evolutionary time. Thus, bifunctional proteins can provide particularly reliable markers for small (recent origin), intermediate, and large (ancient origin) phylogenetic clusters.     

Ribonuclease III: new sense from nuisance.

RNases play an important role in the processing of precursor RNAs, creating the mature, functional RNAs. The ribonuclease III family currently is one of the most interesting families of endoribonucleases. Surprisingly, RNase III is involved in the maturation of almost every class of prokaryotic and eukaryotic RNA. We present an overview of the various substrates and their processing. RNase III contains one of the most prominent protein domains used in RNA-protein recognition, the double-stranded RNA binding domain (dsRBD). Progress in the understanding of this domain is summarized. Furthermore, RNase III only recently emerged as a key player in the new exciting biological field of RNA silencing, or RNA interference. The eukaryotic RNase III homologues which are likely involved in this process are compared with the other members of the RNase III family.     

Formin-like 1 (FMNL1) Is Regulated by N-terminal Myristoylation and Induces Polarized Membrane Blebbing

The formin protein formin-like 1 (FMNL1) is highly restrictedly expressed in hematopoietic lineage-derived cells and has been previously identified as a tumor-associated antigen. However, function and regulation of FMNL1 are not well defined. We have identified a novel splice variant (FMNL1γ) containing an intron retention at the C terminus affecting the diaphanous autoinhibitory domain (DAD). FMNL1γ is specifically located at the cell membrane and cortex in diverse cell lines. Similar localization of FMNL1 was observed for a mutant lacking the DAD domain (FMNL1ΔDAD), indicating that deregulation of autoinhibition is effective in FMNL1γ. Expression of both FMNL1γ and FMNL1ΔDAD induces polarized nonapoptotic blebbing that is dependent on N-terminal myristoylation of FMNL1 but independent of Src and ROCK activity. Thus, our results describe N-myristoylation as a regulative mechanism of FMNL1 responsible for membrane trafficking potentially involved in a diversity of polarized processes of hematopoietic lineage-derived cells.     

The 'Gut index', a new parameter to measure the gross nutritional state of arctic char, Salvelinus alpinus (L.) and brown trout, Salmo trutta L.

The main energy reserves in brown trout, Salmo trutta and Arctic char, Salvelinus alpinus are located in the abdominal cavity and the musculature. The energy content of the rest of the intestines after removal of the gonads, swim bladder, and liver is a good parameter to assess the gross nutritional state of Arctic char and brown trout. This method is laborious, but analysing the dry matter fraction (or the water content) of the same organs instead of their energy content is a practical alternative. The dry matter fraction of these organs expressed as a percentage of its wet weight is here called the 'Gut index'.     

Identification of Cell Cycle Dependent Interaction Partners of the Septins by Quantitative Mass Spectrometry

The septins are a conserved family of GTP-binding proteins that, in the baker''s yeast, assemble into a highly ordered array of filaments at the mother bud neck. These filaments undergo significant structural rearrangements during the cell cycle. We aimed at identifying key components that are involved in or regulate the transitions of the septins. By combining cell synchronization and quantitative affinity-purification mass-spectrometry, we performed a screen for specific interaction partners of the septins at three distinct stages of the cell cycle. A total of 83 interaction partners of the septins were assigned. Surprisingly, we detected DNA-interacting/nuclear proteins and proteins involved in ribosome biogenesis and protein synthesis predominantly present in alpha-factor arrested that do not display an assembled septin structure. Furthermore, two distinct sets of regulatory proteins that are specific for cells at S-phase with a stable septin collar or at mitosis with split septin rings were identified.Complementary methods like SPLIFF and immunoprecipitation allowed us to more exactly define the spatial and temporal characteristics of selected hits of the AP-MS screen.     

Mutagenic activity of nine N,N-disubstituted hydrazines in the Salmonella/mammalian microsome assay.

The mutagenic activity of N,N-dimethyl-, N,N-diethyl-, N,N-dibutyl-, N,N-diisobutyl-, N,N-di(p-tolyl)-, N-ethyl-N-phenyl-, N,N-dibenzyl-, N,N-diphenyl- and N,N-diisopropylhydrazine was examined in the Salmonella/mammalian microsome assay using the strains TA1535, TA1537, TA97, TA98, TA100, TA102 and TA1530. All nine hydrazines were mutagenic in at least one tester strain, although of borderline significance for some of the compounds. The mutagenic potencies of the hydrazines varied 2-3 orders of magnitude, from very weak to moderate mutagenic activity. In general, the addition of S9 resulted in a lowering of the mutagenic activity and a lowering of the toxic properties of the hydrazines. The test results were relatively difficult to evaluate due to toxic effects of many of the test compounds on the test bacteria which may have resulted in an underestimation of the mutagenic potencies of some of the compounds. The pattern of mutagenic activity of the hydrazines in the different tester strains indicates that more than one mechanism of action may be involved in the mutagenicity.