Deoxyribonucleic acid-directed in vitro synthesis of ilv-specific messenger ribonucleic acid by extracts of Escherichia coli K-12

DNA-directed cell-free protein-synthesizing system of Bacillus subtilis

A cell-free coupled system of transcription and translation using cell extracts from Bacillus subtilis and DNA from phage SP82 has been developed. Under optimum conditions, it incorporated approx. 300 pmol methionine during a 1 h incubation. The activity of the system increased linearly as the concentration of S-150 supernatant fraction protein increased from 125 to 325 microgram per assay. The optimum Mg2+ concentration was 12.5-15 mM. Ribosomes required treatment with DNAase in order to reduce endogenous activity, but the S-150 fraction was kept DNAase-free to prevent degradation of exogenously added DNA. The coupled system was sensitive to inhibitors of RNA and protein synthesis. Kinetic studies showed that the number of pmol of nucleotides present in newly synthesized RNA increased linearly for the first 20-min reaction and that the rate of amino acid incorporation increased linearly for the first 30 min. Polyacrylamide gel electrophoresis of the in vitro synthesized products yielded a band pattern that closely resembled the pattern of early phage SP82 proteins produced in vivo.

In vitro synthesis of beta-galactosidase with ilv-lac fusion deoxyribonucleic acid as template

An in vitro protein-synthesizing system has been developed to study the mechanism of induction of ilvC gene in Escherichia coli strain K-12. Deoxyribonucleic acid (DNA) from a lambda phage carrying an ilvC-lac fusion was employed as a template for the in vitro synthesis of beta-galactosidase under the control of the ilvC promoter. The use of this template allowed an investigation of the components required for induction of the ilvC gene and the kinetics of the induction. The in vitro synthesis of beta-galactosidase under the control of the ilvC promoter was found to be DNA, acetohydroxy acid, and guanosine-3'-diphosphate-5'-diphosphate dependent, and sensitive to rifampin, actinomycin D, and chloramphenicol. Uncoupling experiments indicate that the inducer, acetohydroxybutyrate, acts at the transcriptional level. Investigation of a proposed noninducible ilvC regulatory mutant has shown normal induction in vitro. It was also observed that an intact ilvA gene is not required for the induction of the ilvC gene.

Specificity of the stimulation of in vitro ribonucleic acid synthesis by guanosine 5'-diphosphate 3'-diphosphate

The in vitro synthesis of ribonucleic acid (RNA) by S-30 extracts of Escherichia coli K-12 is stimulated from two-to fourfold by 0.16 mM to 0.32 mM guanosine 5'-diphosphate 3'-diphosphate (ppGpp) when either gammacI857St68h80 deoxyribonucleic acid (gammah80 DNA), gammah80dilv DNA or gammah80dlac DNA are employed as templates. Hybridization analysis of the 3H-RNA product transcribed from gammah80dilv DNA in the presence of ppGpp indicates that both bacteriophage- and bacterial-specific transcription is stimulated to an equivalent degree. In the absence of cyclic 3'-5'-adenosine monophosphate (cyclic AMP), correct lac-specifci RNA synthesis from gammah80dlac DNA is not stimulated by 0.32 mM ppGpp although total RNA synthesis is increased nearly twofold. In the presence of 0.5 mM cyclic AMP, correct lacspecific RNA synthesis is stimulated preferentially by ppGpp. These data suggest that ppGpp is capable of stimulating in vitro transcription in both a general and selective manner.