A homolog of the multiple-stress-responsive transcription factor B of Bacillus subtilis was predicted from the DNA sequence analysis of a region of the Staphylococcus aureus chromosome. A hybrid between the coding sequence of the first 11 amino acids of the gene 10 leader peptide of phage T7 (T7.Tag) and the putative sigB gene of S. aureus was constructed and cloned into Escherichia coli BL21(DE3)pLysS for overexpression from a T7 promoter. A homogeneous preparation of the overproduced protein was obtained by affinity chromatography with a T7.Tag monoclonal antibody coupled to agarose. The amino-terminal amino acid sequence of the first 22 residues of the purified protein matched that deduced from the nucleotide sequence. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified protein, designated SB , indicated that it migrated as an approximately 39-kDa polypeptide. Promoter-specific transcription from the B. subtilis B -dependent P B promoter of the sigB operon was stimulated by SB in a concentration-dependent fashion when reconstituted with the S. aureus core RNA polymerase (RNAP). Specific transcript from the predicted B -dependent P B promoter of the sigB operon of S. aureus was obtained by the reconstituted RNAP in a runoff transcription reaction. The sar operon of S. aureus contains three promoter elements (P1, P2, and P3) and is known to partly control the synthesis of a number of extracellular toxins and several cell wall proteins. Our in vitro studies revealed that transcription from the P1 promoter is dependent on the primary factor SA , while that of the P3 promoter is dependent on SB . As determined by primer extension studies, the 5 end of the SB -initiated mRNA synthesized in vitro from the sar P3 promoter is in agreement with the 5 end of the cellular RNA.In prokaryotes, several factors coexist in cells (19,22,24). The transcription factors evolutionarily related to Escherichia coli 70 are subdivided into two groups (15). The primary factor is required for the expression of housekeeping genes whose products are essential for exponential cell growth. The level or the activity of the second group, comprising the alternate factors, has been shown to be modulated in response to environmental and metabolic stresses. The core RNA polymerase (RNAP) associated with a particular factor initiates transcription from a specific set of promoters with conserved sequence motifs. B , identified in sporulating Bacillus subtilis, is the first member of the alternate factors to be reported in prokaryotes (20,21). Much has been learnt recently about the regulation of expression of the sigB operon and the modulation of the function of the SigB ( B ) protein in response to changing stress (entry into stationary growth phase, nutrient depletion, and presence of uncouplers of oxidative phosphorylation) and environmental stress (heat shock and osmotic shock) in B. subtilis (2,6,8,22,36,37,41).The emergence of multiple-drug-resistant, highly pathogenic strains of Staphylococcus aureus poses a serious thr...

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[1] A new approach of constructing deep-penetrating seismic profiles reveals significant, regional variations in crustal thickness under near-constant elevation of Tibet. Over distances of hundreds of kilometers, the crust is as thick as 75 km in southern Tibet but shoals to just over 60 km under the Qiangtang terrane in central Tibet where the deviation from Airy isostasy is equivalent to a thickness of over 10 km in missing crust. Northward thinning of crust occurs gradually over a distance of about 200 km where mechanical deformation, instead of pervasive magmatism, also seems to have disrupted the crust-mantle interface.