Incorporation of p-Fluorophenylalanine into Protein by a Cell-free System

Phenylalanine roles in the seed-to-seedling stage: Not just an amino acid

Phenylalanine is an aromatic amino acid that provides the carbon skeleton for the phenylpropanoid pathway, making many diverse chemicals used for structure, defense, and yet undiscovered functions. The identification of the arogenate dehydratase (ADT) enzymes in the genetic model Arabidopsis thaliana provided a platform to explore the roles of phenylalanine in all stages of life: germination, in the seed-to-seedling transition stage, organelle function, and in generation of defense mechanisms, enabling further studies in other plants. From the literature, data indicate that phenylalanine produced by ADT may have direct roles in organellar and tissue development. Recent studies implicate ADTs in cell division and protection from Reactive Oxygen Species, and in signaling and growth. Research in phenylalanine and subsequent phenylpropanoids also point to a role of phenylalanine as a purveyor of C and N nutrients. The understanding of phenylalanine action in plant cells is enhanced by recent research on phenylalanine in animal cells.

Genetically encoded fluorophenylalanines enable insights into the recognition of lysine trimethylation by an epigenetic reader

Fluorophenylalanines bearing 2-5 fluorine atoms at the phenyl ring have been genetically encoded by amber codon. Replacement of F59, a phenylalanine residue that is directly involved in interactions with trimethylated K9 of histone H3, in the Mpp8 chromodomain recombinantly with fluorophenylalanines significantly impairs the binding to a K9-trimethylated H3 peptide.

Demonstration of an altered phenylalanyl-tRNA synthetase in an analogue-resistant mutant of Aspergillus nidulans

We have isolated and characterized a new class of p-fluorophenylalanine (FPA)-resistant mutant in Aspergillus nidulans using a phenA strain as the wild type, by optimizing the conditions of growth. All four spontaneous mutants selected on a medium containing FPA were found to be recessive to their wild-type alleles in heterozygous diploids. Complementation analyses and linkage data showed that they were allelic and mapped at a single locus (fpaU) in the facA-riboD interval on the right arm of linkage group V. Partial purification and characterization of Phe-tRNA synthetase from wild-type and mutant strains revealed that the mutant enzyme had a greatly reduced ability to activate the analogue. It is suggested that mutation in the fpaU gene brings about a structural alteration in Phe-tRNA synthetase.

Mechanism of irreversible inactivation of phenylalanine-4- and tryptophan-5-hydroxylases by [4-36Cl, 2-14C]p-chlorophenylalanine: a revision

Intraperitoneal injection of [4-36Cl, 2-14C]p-chlorophenylalanine (pCPA) (300 mg/kg) in rats revealed absence of chlorine in pure hepatic phenylalanine hydroxyase, while the carbon label appeared a 1--4 moles/mole of [14C]tyrosine in the inactivated phenylalanine and cerebral tryptophan-5-hydroxylase. Crystalline muscle aldolase and tyrosine hydroxylase also revealed the presence of [2-14C]tyrosine from [2-14C]pCPA without inactivating these enzymes. Injection of L-[(U)-14C] tyrosine led to its incorporation into the above enzymes, but to a different degree without altering the enzyme activity. Repeated injections of p-chlorophenylacetic acid had no effect on phenylalanine or tryptophan-hydroxylase, Administration of pCPA did not change the levels of cerebral biopterins. Reexamination of the effect of cycloheximide on reversing enzymic inactivation by pCPA failed to confirm our earlier observation.

Effect of fluorophenylalanine on bacteriophage MS2 replication

A concentration of 10 mug of fluorophenylalanine per ml added to a chemically defined medium reduced by 100-fold the number of bacteriophage MS2 produced on Escherichia coli C3000 and increased the latent period. Fluorophenylalanine was most effective when added concurrent with infection. Addition of a 10-fold greater concentration of phenylalanine reversed the inhibition caused by fluorophenylalanine. Radioactive fluorophenylalanine was incorporated into the coat protein. The four phenylalanine-containing chymotryptic peptides are not equally accessible to fluorophenylalanine. Only two of the peptides are highly labeled by fluorophenylalanine. Incorporation of fluorophenylalanine decreased the specific infectivity and the rate of adsorption but did not increase the sensitivity of the whole virus to ribonuclease. MS2 ribonucleic acid (RNA) functioned as messenger RNA for the incorporation of both phenylalanine and fluorophenylalanine in a cell-free incorporating system from E. coli.

Membrane alteration and the formation of metachromatic granules in Escherichia coli treated with p-fluorophenylalanine

The effect of p-fluorophenylalanine (FPA) on growing cultures of Escherichia coli was studied with regard to the composition and morphology of the cell envelope. A cell wall fraction was prepared by autolysis in hypertonic medium, and the resulting spheroplasts were osmotically lysed to obtain a cytoplasmic membrane fraction. Incorporation of labeled phenylalanine, FPA, and N-acetylglucosamine into both fractions of FPA-inhibited cells suggested that the composition of the membrane changed with time, whereas that of the cell wall remained relatively constant. Amino acid analysis revealed changes in the composition of the membrane fraction after FPA inhibition. Electron micrographs of shadowed cells and membranes revealed the presence of electron-dense metachromatic granules during the early stages of FPA inhibition.