Synthesis of bacteriophage lambda proteins in vitro

Transcription antitermination in vitro by lambda N gene product: requirement for a phage nut site and the products of host nusA, nusB, and nusE genes

Employing specifically engineered plasmids in which the expression of E. coli galK cistron is regulated by transcription termination, we have analyzed the antitermination function of phage lambda N gene product in S30 extracts. Antitermination by N, dependent on its site of action, nutL, is defective in the extracts prepared from nusA, nusB, and nusE mutants. By complementation analysis, we demonstrate that none of the these nus mutations affects the synthesis of N or the other nus gene products to cause a defect in antitermination. Rather, these mutations have inactivated a set of specific host components, the Nus factors, which are essential for N activity. Curiously, an appreciable portion of N and Nus complementation activities of an S30 extract is ribosome-associated. The significance of this finding remains to be uncovered.

Precolicin E1, the major gene product of plasmid-ColE1 deoxyribonucleic acid in vitro

Coupled transcription and translation of plasmid-ColE1 DNA in vitro under optimized conditions gave one major product. This has an apparent weight of 71 000, the same N-terminal sequence as colicin E1 and was not digested by deoxyribonuclease or ribonuclease. It differed from colicin E1 in its C-terminal residue and amino acid composition. It had lower specific activities in cell killing and in the fluorescence-enhancement in vitro assay of Phillips & Cramer [(1973) Biochemistry 12, 1170--1176] than did colicin E1, but both proteins bound in equimolar amounts to colicin-sensitive and colicin-resistant cells. The product of plasmid-ColE1-DNA-directed protein synthesis was converted into a protein indistinguishable in structure and activity from colicin E1 by incubation in the reaction mixture, after deoxyribonuclease and ribonuclease treatment, for a further 20 h at 37 degrees C. A protein with similar properties to the 71 000-dalton product in vitro was identified in extracts of a ColE1+ colicin-tolerant mutant of Escherichia coli K12. It is concluded that this protein probably represents a pre-form of colicin E1 which may be involved in colicin-E1 secretion or cellular colicin-E1 immunity in colicin-E-producing cells, or both of these processes.

Purification and properties of a lambda operator-binding protein which is expected to be autorepressor (tof protein) from E. coli carrying lambdadv plasmid

In order to study the mode of action of the tof gene product, which is an "autorepressor" of the bacteriophage lambda and plasmid lambdadv, we have purified a DNA-binding protein which is specifically produced in bacteria carrying lambdadv. This protein possesses characteristics expected for the product of the tof gene, since it is produced under conditions where cI-repressor is not made, and since it binds to oL and oR operators on the lambda phage genome. The molecular weight of the native protein is 16,000-17,000 daltons, and the monomeric molecular weight as measured by gel electrophoresis in the presence of sodium dodecyl sulfate is about 10,000 daltons. Denaturation and renaturation experiments demonstrated that the native protein is a dimer of 10,000-dalton monomers. The lambdaDNA-specific binding protein is not produced in cells carrying i21dv or ø80dv.

Clo DF13 plasmid deoxyribonucleic acid-directed in vitro synthesis of biologically active cloacin DF13 and clo DF13 immunity protein

Clo DF13 plasmid deoxyribonucleic acid (DNA) was used as a template to direct transcription and translation in a DNA-dependent cell-free system prepared from Escherichia coli. Analysis of the invitro products on sodium dodecylsulfate-polyacrylamide gels revealed that Clo DF13 DNA directs the synthesis of at least 10 polypeptides ranging in molecular weight from approximately 7,000 to 70,000. Two of these polypeptides could be identified, with respect to their physiochemical and biological characteristics, as the products of the Clo DF13 genes coding for cloacin DF13 and Clo DF13 immunity protein. These results confirm previous findings, obtained which Clo DF13-harbouring minicells of E. coli, that the structural tenes for the latter proteins residue on the Clo DF13 genome.

Synthesis of mitochondrial proteins in an Escherichia coli cell-free system directed by yeast mitochondrial DNA

The optimum conditions for transcription in vitro of yeast mtDNA into biologically relevant RNA by Escherichia coli RNA polymerase holoenzyme and yeast mitochondrial RNA polymerase was found to critically depend on salt concentration. RNA was transcribed (at 0.25 M KCl concentration) from high-molecular-weight mtDNA which was then translated in an E. coli (S-30) cell-free protein synthesising system. Efficient translation of mitochondrial RNA was achieved using conditions which had also been determined to be optimal in other systems. Identification of the polypeptides produced in the translation system was made using antiserum raised against mitochondrial membranes. Electrophoresis of the completely dissociated antigen-antibody complexes using dodecylsulphate-polyacrylamide gels revealed that the system in vitro produced polypeptides of similar molecular weight to those synthesised in vivo by cycloheximide-inhibited whole cells.

Repression and autogenous stimulation in vitro by bacteriophage lambda repressor

Purified lambda repressor protein is shown to reduce the lambda DNA-directed synthesis of proteins in vitro as determined both by net amino-acid incorporation and by analysis of specific lambda-coded proteins resolved by sodium dodecyl sulfate/polyacrylamide slab gel electrophoresis. By means of different lambda DNA templates carrying deletion and point mutations in the operators o-L or o-R, it has been possible to demonstrate repression of the synthesis of two classes of lambda proteins. The synthesis of one, class c, appears to be controlled from the operator o-L and is more efficiently repressed at low concentrations of the repressor than that of the other class of repressible lambda proteins, class d, which is controlled from the operator o-R. Several other proteins synthesized in vitro are not repressible. Some of these are coded by the J-att region. In addition, the repressor appears to have another activity, that of stimulating the synthesis of a protein identified as the repressor itself. Lambda repressor appears to stimulate its own synthesis by acting at prm, a site defined by the cis-acting mutation prm 116.

Identification and characterization of the in vitro synthesized gene products of bacteriophage M13

Bacteriophage M13 replicative form (RF) DNA was used to direct coupled transcription and translation in cell-free extracts prepared from Escherichia coli. By using RF DNA, isolated from cells infected with appropriate amber mutants of this phage, it has been possible to identify the products of genes I through IV. By using the same methods no gene-product relationship could be demonstrated for genes VI and VII. Coupled in vitro protein synthesis studies on RF-III DNA, a linear double-stranded DNA molecule, obtained after cleavage of either RF-I or RF-II DNA with the restriction endonuclease R.Hin11 from Haemophilus influenzae, indicated that the cleavage site for this enzyme is located in gene II. The in vitro products of both gene III and gene VIII are about 30 and six amino acids longer, respectively, than their native counterparts present within the virion. These results suggest that the latter proteins arise in vivo by cleavage of precursor molecules. Coupled transcription and translation studies on a DNA fragment which only contained the genetic information coding for gene IV protein, obtained after cleavage of RF DNA with the restriction endonuclease R.Hap11 from Haemophilus aphirophilus, indicated that a large number of the in vitro synthesized polypeptides are the result of premature chain termination.

Synthesis of diphtheria tox-gene products in Escherichia coli extracts

In a protein-synthesizing system extracted from E. coli, purified DNA from corynephages betac(tox+) and beta45c was used to direct the in vitro synthesis of diphtheria toxin and of the related nontoxic protein, CRM45, as well as of other beta-phage proteins. When betac(tox+)-DNA or betac-DNA was added to a similar system extracted from the nonlysogenic Corynebacterium diphtheriae strain, C7(s)(-)(tox-), neither toxin nor the CRM45 protein was produced, although other beta-phage proteins were synthesized in amounts equivalent to those produced in the E. coli system from the same amount of beta-phage DNA. Preliminary experiments suggest that both toxinogenic and nontoxinogenic strains of the diphtheria bacillus contain a factor that specificially blocks expression of the tox gene. Synthesis of toxin and the CRM45 protein in the E. coli system could not be inhibited by relatively high concentrations of inorganic iron, but could be inhibited by extracts from the C7(s)(-)(tox-) strain of C. diphtheriae.

Multiple repressor binding at the operators in bacteriophage lambda

Short DNA duplexes are protected when lambda DNA is digested with nuclease in the presence of lambda repressor. As the ratio of repressor to operator is increased, six successively larger fragments are recovered, ranging in size from 35 to 100 base pairs, each of which binds repressor. Study of these fragments indicates that, at each of the two lambda operators (o(L) and o(R)), repressor first binds to a unique site (not necessarily terminal), and that five additional sites are then filled in linear right-ward or left-ward order. The nucleotide sequences and affinities for repressor of o(L) and o(R) are not identical, although six fragments of similar size are protected at each operator. Evidence is presented arguing against the existence of hairpin-like structures in the operator fragments, and, moreover, it is shown that the operator duplex does not unwind when repressor binds to it.