Serine kinase activity of a Bacillus subtilis switch protein is required to transduce environmental stress signals but not to activate its target PP2C phosphatase

The RsbT serine kinase has two known functions in the signal transduction pathway that activates the general stress factor σ^B of Bacillus subtilis . First, RsbT can phosphorylate and inactivate its specific antagonist protein, RsbS. Second, upon phosphorylation of RsbS, RsbT is released to stimulate RsbU, a PP2C phosphatase, thereby initiating a signalling cascade that ultimately activates σ^B. Here we describe a mutation that separates these two functions of RsbT. Although the mutant RsbT protein had essentially no kinase activity, it still retained the capacity to stimulate the RsbU phosphatase in vitro and to activate σ^B when overexpressed in vivo . These results support the hypothesis that phosphatase activation is accomplished via a long-lived interaction between RsbT and RsbU. In contrast, RsbT kinase activity was found to be integral for the transmission of external stimuli to σ^B. Thus, one route by which environmental stress signals could enter the σ^B network is by modulation of the RsbT kinase activity, thereby controlling the magnitude of the partner switch between the RsbS–RsbT complex and the RsbT–RsbU complex.     

Osmoregulation in Streptomyces coelicolor: modulation of SigB activity by OsaC

As free-living non-motile saprophytes, Streptomyces need to adapt to a wide range of environmental conditions and this is reflected by an enormous diversity of regulatory proteins encoded by, for example, the genome of the model streptomycete Streptomyces coelicolor . In this organism, we have identified a new osmoregulation gene, osaC , encoding a member of a novel family of regulatory proteins. Members of the family have a predicted domain composition consisting of an N-terminal kinase domain related to anti-sigma factors, sensory Pas and Gaf domains, and a C-terminal phosphatase domain. osaC is linked to the response regulator gene osaB ; expression analysis of the latter revealed that it is induced after osmotic stress in a σ^B-dependent manner. OsaC is required to return osaB and sigB expression back to constitutive levels after osmotic stress. From analysis of the activities of OsaC_ΔPho, lacking the C-terminal phosphatase domain, and OsaC_N92A, with a substitution of a critical asparagine residue in the kinase domain, we infer that this N-terminal domain functions as a σ^B anti-sigma factor. Indeed, co-purification experiments indicate association of OsaC and σ^B. These results support a model for post-osmotic stress modulation of σ^B activity by OsaC.     

A new RNA polymerase sigma factor, σF is required for the late stages of morphological differentiation in Streptomyces spp.

A gene ( sigF ) encoding a new sigma factor was isolated from Streptomyces aureofaciens using a degenerate oligonucleotide probe designed from the GLI(KDNE)A motif lying within the well-conserved region 2.2 of the eubacterial σ⁷⁰ family. Homologues were present in other Streptomyces spp., and that of the genetically well-studied Streptomyces coelicolor A3(2) was also cloned. The nucleotide sequences of the two sigF genes were determined and shown to encode primary translation products of 287 ( S. coelicolor ) and 295 ( S. aureofaciens ) amino acid residues, both showing greatest similarity to σ^B of Bacillus subtilis . However, while σ^B is involved in stationary-phase gene expression and in the general stress response in B. subtilis , σ^F affects morphological differentiation in Streptomyces , Disruption of sigF did not affect vegetative growth but did cause a whi mutant phenotype. Microscopic examination showed that the sigF mutant produced spores that were smaller and deformed compared with those of the wild type, that the spore walls were thinner and sensitive to detergents and that in sigF mutant spores the chromosome failed to condense. σ^F is proposed to control the late stages of spore development in Streptomyces .     

Serum amylase 2 polymorphism in pigs

A genetic polymorphism of the pig amylase 2 system is described. It is controlled by two codominant genes, Am 2^A and Am 2^B. A comparison of some breeds from Byelorussian breeding farms gives the following frequencies for the alleles Am 2^A and Am 2^B , respectively: 0.35 and 0.865 in Large White (n = 682), 0.257 and 0.743 in Byelorussian Black and White (n = 400), 0.540 and 0.460 in Hampshire (n = 51).
While studying the genotype distribution according to the Hardy-Weinberg law, a genetic imbalance in Byelorussian Black and White pigs was established (χ²= 56.4). Genetic relationship between the Am 1 and Am 2 loci was not found.     

Genetic polymorphism of leucine aminopeptidase in canine plasma

Genetic polymorphism was found in the isozymes of leucine aminopeptidase in the canine plasma. Analysis of parentage records of the dogs examined revealed that the phenotypic variation of leucine aminopeptidase isozymes was controlled by one autosomal locus, designated Lap , with two codominant gene alleles, Lap ^A and Lap ^B, though individuals of homozygous B type were not found in the specimen used. The gene frequencies were 0.97 for Lap ^A and 0.03 for Lap ^B in most of the dog breeds examined. Higher frequencies for Lap ^B (0.11–0.25) were obtained in breeds such as Pointer, Doberman pinscher, Boxer, Borzoi and San'in-Shiba (a Japanese native breed), while in German shepherd, Collie, and two of the Japanese native breeds, Akita and Kishu, phenotype of the isozyme seemed to be fixed to homozygous A ( Lap ^A/ Lap ^A).     

Acid stress activation of the σE stress response in Salmonella enterica serovar Typhimurium

The alternative sigma factor σ^E is activated by unfolded outer membrane proteins (OMPs) and plays an essential role in Salmonella pathogenesis. The canonical pathway of σ^E activation in response to envelope stress involves sequential proteolysis of the anti-sigma factor RseA by the PDZ proteases DegS and RseP. Here we show that σ^E in Salmonella enterica sv. Typhimurium can also be activated by acid stress. A σ^E-deficient mutant exhibits increased susceptibility to acid pH and reduced survival in an acidified phagosomal vacuole. Acid activation of σ^E-dependent gene expression is independent of the unfolded OMP signal or the DegS protease but requires processing of RseA by RseP. The RseP PDZ domain is indispensable for acid induction, suggesting that acid stress may disrupt an inhibitory interaction between RseA and the RseP PDZ domain to allow RseA proteolysis in the absence of antecedent action of DegS. These observations demonstrate a novel environmental stimulus and activation pathway for the σ^E regulon that appear to be critically important during Salmonella –host cell interactions.     

Studies on bovine serum amylase; evidence for two loci

Two genetically controlled polymorphic systems of amylase enzymes are described in sera from Friesian, Jersey, Guernsey, Hereford, Ayrshire and Charolais cattle. One of these Ami has been described previously and is controlled by two codominant alleles in British cattle, AmI ^B and AmI ^C. Evidence presented here suggests that it could be a gamma.amylase. The other enzyme which is described here for the first time has many of the properties of an alpha amylase. It is also polymorphic and controlled by two codominant alleles AmII ^A and AmII ^B. AmII ^A is only present in low frequency. The inheritance of both enzyme systems has been studied in 419 families.