Dynamics of the 16O(e, e'p) reaction at high missing energies.

We measured the cross section and response functions for the quasielastic 16O(e,e'p) reaction for missing energies 25< or =E(m)< or =120 MeV at missing momenta P(m)< or =340 MeV/c. For 25

Role of interactions between SpoIIAA and SpoIIAB in regulating cell-specific transcription factor sigma F of Bacillus subtilis.

Genetic experiments have suggested that sigma F, the first compartment-specific transcription factor in sporulating B. subtilis, is regulated by an anti-sigma factor SpoIIAB and an anti-anti-sigma factor SpoIIAA. Previously, we reported biochemical results demonstrating that SpoIIAB is both a phosphokinase whose substrate is SpoIIAA and an inhibitor of sigma F-directed transcription. We now show that in the presence of SpoIIAB and ATP or ADP, SpoIIAA can undergo two alternative reactions. When ATP is present, SpoIIAA is phosphorylated rapidly and completely to SpoIIAA-phosphate, and SpoIIAB is immediately released; but in the presence of ADP, SpoIIAA forms a long-lasting complex with SpoIIAB. ADP is an inhibitor of the phosphorylation by ATP. Furthermore, we have mutated SpoIIAA at residue Ser 58, the target for phosphorylation, to aspartate or alanine. SpoIIAAS58D, which apparently resembles SpoIIAA-phosphate, is unable to make a complex with SpoIIAB and is devoid of anti-anti-sigma F activity, whereas SpoIIAAS58A, which cannot be phosphorylated, makes complexes with SpoIIAB in the presence of ADP or ATP and has constitutive anti-anti-sigma F activity both in vivo and in vitro. It seems likely that the alternative reactions of SpoIIAA and SpoIIAB, involving ADP or ATP, regulate the anti-anti-sigma capacity of SpoIIAA and hence the activity of sigma F.

Sigma F, the first compartment-specific transcription factor of B. subtilis, is regulated by an anti-sigma factor that is also a protein kinase.

The establishment of compartment-specific transcription in sporulating cells of B. subtilis is governed at the level of the activity of transcription factor sigma F. Genetic experiments have suggested that SpoIIAA and SpoIIAB, the other products of the sigma F operon, are involved in regulating sigma F activity. This activity is inhibited in the predivisional cell but specifically released from inhibition in the prespore about 1.5 hr after sporulation is induced. We now show that purified SpoIIAB inhibits transcription directed by sigma F in vitro. We note that the amino acid sequence of SpoIIAB shows some similarity to a group of bacterial histidine protein kinases, and we find that SpoIIAB is indeed a protein kinase that phosphorylates SpoIIAA on a serine residue. We suggest that this phosphorylation is responsible for the compartment-specific release of sigma F activity, perhaps through the formation of a tight complex between SpoIIAB and phosphorylated SpoIIAA.

Genetic suppression analysis of sigma E interaction with three promoters in sporulating Bacillus subtilis.

Genetic evidence suggests that the sigma (sigma) subunit of RNA polymerase determines the specificity of promoter utilization, by making sequence-specific contacts with DNA. We examined the effects of two single amino acid(aa) substitutions in sigma E on the utilization of mutated derivatives of three different promoters in sporulating Bacillus subtilis. We found allele-specific suppression of mutations in all three promoters by each aa substitution in sigma E. These results provide strong evidence that sigma E interacts with each of these promoters in vivo. Moreover, the specificity of suppression of the mutations by the aa substitutions in sigma E lead us to speculate that the Met124 of sigma E closely contacts two adjacent bp in the -10 region of the promoters.