Developmental expression of three proteins from the first gene of the RNA polymerase sigma 43 operon of Bacillus subtilis

A novel Bacillus subtilis gene, antE, temporally regulated and convergent to and overlapping dnaE

A Bacillus subtilis promoter, Px, that functions in a convergent manner with the sigA operon promoter P3 has been found in the sigA operon. Promoter Px is turned on at the same time as promoter P3 during early sporulation. The transcript from promoter Px codes for a small protein with partial homology to the OmpR protein from Escherichia coli and also carries an untranslated sequence at its 3' end that is complementary to the 5' end of the P3 transcript, which codes for the ribosome binding site of dnaE. The gene controlled by Px has been called antE. The expression of antE does not require sigmaB, sigmaE, or sigmaH. Px was transcribed in vitro by the sigmaA holoenzyme and is the seventh promoter to be recognized in the sigmaA operon. A possible role for the antE gene during early sporulation is proposed.

Expression and secretion of heterologous proteases by Corynebacterium glutamicum

Genes encoding the basic protease of Dichelobacter nodosus (bprV) and the subtilisin of Bacillus subtilis (aprE) were cloned and expressed in Corynebacterium glutamicum. In each case, enzymatically active protein was detected in the supernatants of liquid cultures. While the secretion of subtilisin was directed by its own signal peptide, the natural signal peptide of the bprV basic protease did not facilitate secretion. A hybrid aprE-bprV gene in which the promoter and signal peptide coding sequences of subtilisin replaced those of bprV could be expressed, and basic protease was secreted by C. glutamicum. Expression of these proteases in C. glutamicum provides an opportunity to compare protein secretion from this gram-positive host with that from other gram-positive and gram-negative bacteria.

The sigma factors of Bacillus subtilis

The specificity of DNA-dependent RNA polymerase for target promotes is largely due to the replaceable sigma subunit that it carries. Multiple sigma proteins, each conferring a unique promoter preference on RNA polymerase, are likely to be present in all bacteria; however, their abundance and diversity have been best characterized in Bacillus subtilis, the bacterium in which multiple sigma factors were first discovered. The 10 sigma factors thus far identified in B. subtilis directly contribute to the bacterium's ability to control gene expression. These proteins are not merely necessary for the expression of those operons whose promoters they recognize; in many instances, their appearance within the cell is sufficient to activate these operons. This review describes the discovery of each of the known B. subtilis sigma factors, their characteristics, the regulons they direct, and the complex restrictions placed on their synthesis and activities. These controls include the anticipated transcriptional regulation that modulates the expression of the sigma factor structural genes but, in the case of several of the B. subtilis sigma factors, go beyond this, adding novel posttranslational restraints on sigma factor activity. Two of the sigma factors (sigma E and sigma K) are, for example, synthesized as inactive precursor proteins. Their activities are kept in check by "pro-protein" sequences which are cleaved from the precursor molecules in response to intercellular cues. Other sigma factors (sigma B, sigma F, and sigma G) are inhibited by "anti-sigma factor" proteins that sequester them into complexes which block their ability to form RNA polymerase holoenzymes. The anti-sigma factors are, in turn, opposed by additional proteins which participate in the sigma factors' release. The devices used to control sigma factor activity in B, subtilis may prove to be as widespread as multiple sigma factors themselves, providing ways of coupling sigma factor activation to environmental or physiological signals that cannot be readily joined to other regulatory mechanisms.

Use of a gram- signal peptide for protein secretion by gram+ hosts: basic protease of Dichelobacter nodosus is produced and secreted by Bacillus subtilis

The bprV gene, encoding the extracellular basic protease of the Gram- anaerobic bacterium Dichelobacter nodosus, was expressed and the protein secreted in Bacillus subtilis using the novel cloning/expression vector pNC3 [Wu et al., Gene 106 (1991) 103-107]. The pre- and pro-peptides were processed correctly in this heterologous system, and the 127-amino acid C-terminal extension region was also removed. The recombinant gene product was indistinguishable biochemically or immunochemically from the authentic protease and was able to form crystals upon dialysis, as was found for the authentic protease. This is the first example of the direct secretion of a Gram- extracellular enzyme in B. subtilis via its own signal peptide. The fact that this gene can be expressed and its product secreted in both Escherichia coli and B. subtilis provides a unique opportunity to study and compare the similarities and differences in protein secretion between Gram- and Gram+ organisms.

Development of a novel Bacillus subtilis cloning system employing its neutral protease as screen marker

Part of the pUC19 polylinker sequence (33 bp) was inserted into the pro-peptide-coding region of the Bacillus subtilis neutral protease-encoding gene to replace a 93-bp FspI-HindIII fragment. This in-frame sequence replacement had little effect on the expression and secretion of the neutral protease. This plasmid can therefore be used as a cloning vector, and recombinant clones can be directly identified on skim milk indicator plates by the loss of a clear ring (or halo) around the colonies. This novel cloning system offers several advantages over existing B. subtilis cloning vectors: (i) convenient direct screening of recombinants; (ii) the use of inexpensive indicator; (iii) no restriction on the use of host strains; and (iv) the availability of seven frequently used unique cloning sites: BamHI, XbaI, SalI, PstI, SphI, HindIII, and EcoRI. This system also has the potential to be used as an expression/secretion vector.

Transposon Tn917lacZ mutagenesis of Bacillus subtilis: identification of two new loci required for motility and chemotaxis

We have used Tn917lacZ to mutagenize the Bacillus subtilis chromosome and have isolated mutants that are defective in chemotaxis and motility. Mapping of the transposon inserts identified two new loci. Mutations in one of these loci generated mutants that had paralyzed flagella. Accordingly, we designate this a mot locus. The other locus is closely linked to the first and encodes proteins specifying chemotaxis functions. This locus is designated the cheX locus. Both the mot and cheX loci map close to ptsI. An additional transposon insert that maps in the hag locus was obtained. The pattern of beta-galactosidase expression from some of the transposons suggested that the mot locus is regulated by sigD, a minor sigma factor of B. subtilis. The cheX locus appeared to be under the control of vegetative sigA. Four transposon inserts were mapped to a previously characterized che locus near spcB. These mutants did not produce flagellin and were defective in the methylation of the methyl-accepting chemotaxis proteins. This locus probably encodes proteins required for flagellum biosynthesis and other proteins that are required for the methylation response.

Multiple active forms of a novel serine protease from Bacillus subtilis

We have cloned and sequenced a gene (epr) encoding a novel serine protease from Bacillus subtilis. Several active forms of the enzyme with molecular masses between 40 and 34 kDa were found in the medium of B. subtilis cultures containing the epr gene cloned on a plasmid. Deletions at the 3' end of the gene, removing up to 240 amino acids of the reading frame, abolished the expression of the larger species but did not affect the expression of the 34 kDa enzyme. The C-terminal third of the protein is therefore not required for protease activity. The size variation of the active forms expressed by the complete epr gene appears to be the result of partial removal of the C-terminus either by processing or degradation. Thus, the epr gene consists of two domains, one encoding a serine protease homologous to subtilisin and the other a C-terminus of unknown function.

A mutation in P23, the first gene in the RNA polymerase sigma A (sigma 43) operon, affects sporulation in Bacillus subtilis

Mutations within P23, the first gene of the Bacillus subtilis sigma A operon, were not detrimental to vegetative growth or sporulation. One deletion of P23 resulted in a strain that sporulated earlier than the wild type. This aberrant phenotype may be due to the simultaneous deletion of a sigma H promoter from the sigma A operon.

Defects in the nutrient-dependent methylation of a membrane-associated protein in spo mutants of Bacillus subtilis

Methylation of a membrane-associated protein with an apparent molecular mass of 40,000 daltons has been observed in Bacillus subtilis. The methylation was nutrient dependent and occurred with a doubling time of 4 +/- 1 min. In wild-type strains, the half-life of turnover of the methyl group(s) was 17 +/- 6 min. Several isogenic strains of B. subtilis containing spo0 mutations (spo0A and spo0H) were found to be normal in glutamate-dependent methylation of the protein and turnover of the methyl group(s). In strains containing spo0B and spo0E mutations, the methyl group(s) were incorporated in response to glutamate addition but turnover was not at a normal rate. The half-life of methyl group turnover was extended to 45 +/- 3 min in these strains. In a spo0K mutant and in spoIIJ and spoIIF mutants, the protein was not significantly methylated. The methylation of a 40,000 dalton protein was also found to be dependent on phosphate. This methylation was observed in wild-type and spo0A and spo0H strains with a doubling time of 4 +/- 1 min and a half-life of turnover of the methyl group(s) of 11 +/- 3 min. In strains containing spo0B, spo0E, and spo0F mutations, the phosphate-dependent incorporation of the methyl group(s) was normal (5 +/- 1 min) but the turnover half-life was extended to 46 +/- 8 min. It is not known whether the nitrogen-dependent and phosphate-dependent systems methylated the same protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Bluetongue virus-17 fusion protein ns1 expressed in Escherichia coli by pUC vectors

The cDNA coding for the major nonstructural protein, NS1, of bluetongue serotype 17 (BTV-17) was cloned previously. Using pUC plasmids, we have successfully expressed the NS1 protein in Escherichia coli as a LacZ-NS1 fusion protein. The recombinant NS1 protein reacted with rabbit anti-BTV-17 antiserum, and was thus immunologically indistinguishable from the native BTV-17 NS1 protein. This was the first bluetongue viral protein to be produced in a bacterial system.

Expression and secretion of human atrial natriuretic alpha-factor in Bacillus subtilis using the subtilisin signal peptide

Using the signal peptide of the Bacillus subtilis subtilisin gene (aprE) and a synthetic cDNA corresponding to the mature region of the human atrial natriuretic alpha-factor (hANF), we have constructed a secretion vector. B. subtilis cells, when transformed with this vector, secrete immunoreactive hANF peptides into the medium at about 500 micrograms/liter. The hANF is the first human gene product to be secreted from B. subtilis using this signal peptide. We have used promoters active during vegetative growth or sporulation and hosts deficient in several extracellular proteases but some proteolysis of the secretion products still occurs. In addition, both cell growth and sporulation are adversely affected by hANF production. Possible explanations for this observation are inefficient secretion of the atrial hormone or toxicity of the precursor or mature peptide.

Nutrient-stimulated methylation of a membrane protein in Bacillus licheniformis

When nitrogen-starved vegetative cells of Bacillus licheniformis A5 were presented with a good nitrogen source in the presence of chloramphenicol and methyl-labeled methionine, a 40-kilodalton (kDa) protein was found to be reversibly methylated, with a half-life of approximately 10 to 15 min. The 40-kDa protein was strongly methylated in response to the addition of ammonia, glutamine, or sodium glutamate nitrogen sources that produce generation times of less than or equal to 90 min) but was very poorly methylated in the absence of a nitrogen source or in the presence of potassium glutamate or histidine (generation times of greater than 150 min). The methylated protein was found to be membrane associated, but the methylation reaction did not appear to be related to chemotaxis, because the spectrum of nutrients that promoted methylation was different from that which prompted a chemotactic response. In addition, the methyl residue on the 40-kDa protein was found to be alkali stable. Approximately 180 to 640 molecules of the methylated protein were found per cell. The characteristics of this methylated protein were consistent with the hypothesis that the reversible methylation of the protein functions in nutrient sensing to regulate growth, cell division, and the initiation of sporulation.

rpoD operon promoter used by sigma H-RNA polymerase in Bacillus subtilis

Three promoters direct transcription of the sigA (rpoD) operon in Bacillus subtilis. Promoters P1 and P2 are used during the exponential growth phase, whereas P3 is used only during the stationary phase. We examined the use of these promoters in promoter-probe plasmids and found that expression from P3 was prevented by a mutation in spoOH, which encodes the secondary RNA polymerase sigma factor sigma H. Moreover, we found that sigma H-containing RNA polymerase efficiently and accurately used the P3 promoter in vitro. Evidently, this operon, which is essential for exponential growth, is transcribed during the early phase of sporulation by this secondary form of RNA polymerase. Comparison of the nucleotide sequences of the P3 promoter and the spoVG promoter, which also is used by sigma H-RNA polymerase, revealed sequences at the -10 and -35 regions of these promoters that may signal recognition of promoters by sigma H-RNA polymerase.