Predicted class-I aminoacyl tRNA synthetase-like proteins in non-ribosomal peptide synthesis

Background  

Recent studies point to a great diversity of non-ribosomal peptide synthesis systems with major roles in amino acid and co-factor biosynthesis, secondary metabolism, and post-translational modifications of proteins by peptide tags. The least studied of these systems are those utilizing tRNAs or aminoacyl-tRNA synthetases (AAtRS) in non-ribosomal peptide ligation.     

Reconstitution of RecBC DNase activity from purified Escherichia coli RecB and RecC proteins

The Escherichia coli RecB protein, normally synthesized in low amounts, has been amplified by linkage of the recB gene to the phage lambda leftward promoter in an expression plasmid. From strains harboring this plasmid, RecB protein has been purified to homogeneity by a simple procedure which includes affinity chromatography on a column of RecC protein bound to agarose. The purified RecB protein has DNA-dependent ATPase activity but no exonuclease activity. RecC protein alone has neither ATPase nor exonuclease activity. However, when combined together, the RecB and RecC proteins show the ATP-dependent double-stranded exonuclease properties characteristic of the RecBC DNase.     

Choline transport in Fusarium graminearum A 3 5

Fusarium graminearum A 3/5 possesses a high affinity system (Km = 32 +/- 8 microM; mean +/- SE) for uptake of choline, which was shown to be energy-dependent and constitutive. The maximum rate of choline uptake by this system was repressed by ammonia and glucose, showing a three-fold increase in maximum activity after nitrogen (2 h) or carbon (4 h) starvation. The system was highly specific for choline with only dimethylethanolamine (Ki = 198 +/- 29 microM), betaine aldehyde (Ki = 95 +/- 14 microM) and chlorocholine (Ki = 352 +/- 40 microM) acting as competitive inhibitors. Hemicholinium-3 acted as a mixed (non-competitive) inhibitor (KIES = 1.9 +/- 0.6 microM; KIE = 3.6 +/- 1.9 microM).     

Induction of spherule formation in Physarum polycephalum by polyols

A method has been developed for inducing spherule formation (spherulation) in the myxomycete Physarum polycephalum by transferring the culture to synthetic medium containing 0.5 m mannitol or other polyols. This morphogenetic process occurred within 12 to 35 hr after the inducer was added. The mature spherules existed as distinct morphogenetic units, in contrast to the clusters of spherules formed during starvation. Ninety per cent of the spherules germinated by 24 hr in synthetic medium. The changes in the synthesis of ribonucleic acid (RNA), deoxyribonucleic acid (DNA), and protein during plasmodial growth, spherulation, and germination of spherules are described. When spherule formation was completed, RNA, protein, and DNA decreased, compared with the values at the beginning of the conversion. The incorporation of (3)H-uridine into trichloroacetic acid-insoluble material was different in each of these periods, and this incorporation was sensitive to actinomycin D. The amount of glycogen increased during growth, whereas it decreased during spherulation. (14)C-glucose could be taken up by the cells in the presence of the inducer, and mannitol could not replace glucose as a source of energy. The mode of action of mannitol and its mechanism of induction are discussed.