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J Davey

Publications and source records attributed to J Davey.

12 recordsLinked to original sources
PubMed1992

Mating pheromones of the fission yeast Schizosaccharomyces pombe: purification and structural characterization of M-factor and isolation and analysis of two genes encoding the pheromone.

Conjugation in the fission yeast Schizosaccharomyces pombe is controlled by the action of mating pheromones. Here I describe the isolation and characterization of M-factor, the pheromone released by M-type cells. M-factor is a nanopeptide in which the carboxy-terminal cysteine residue is carboxy-methylated and S-alkylated, probably with a farnesyl residue: Tyr-Thr-Pro-Lys-Val-Pro-Tyr-Met-Cys(S-farnesyl)-OCH3. Evidence for this structure was obtained by amino acid analysis, mass spectrometry and tandem mass spectrometry of the native M-factor. Two genes encoding the M-factor were also identified and characterized. It appears that M-factor is synthesized as a larger precursor which is post-translationally cleaved and modified to yield the active pheromone. The proposed modifications are consistent with mechanisms known to exist in other yeast and higher eukaryotes.

Amino Acid Sequence↗
PubMed1992

The ras1 function of Schizosaccharomyces pombe mediates pheromone-induced transcription.

Loss of ras1+ function renders fission yeast cells unable to undergo morphological changes in response to mating pheromones, whereas cells carrying activated mutations in ras1 are hyper-responsive. This has led to the suggestion that the ras1 gene product plays a role in mating pheromone signal transduction. Using partially purified M factor we demonstrate that the mat1-Pm gene, which controls entry into meiosis, is transcribed in response to a pheromone signal. Strains mutated in the ras1 gene or in ste6, the fission yeast homologue of Ras protein GDP/GTP exchange factor, are unable to induce transcription of mat1-Pm in response to M factor. Furthermore, an activated ras1val17 mutant exhibits a stronger induction of the mat1-Pm transcript. However, transcription still depends on nitrogen deprivation as well as on the presence of pheromone, showing that activation of the Ras1 protein alone does not substitute for any of these signals. The pat1-114 mutant bypasses the ras1/ste6 checkpoint, suggesting that activation of ras1 contributes to inactivation of the pat1 protein kinase.

Blotting, Northern↗
PubMed1979

The vectorial orientation of human monoamine oxidase in the mitochondrial outer membrane.

1. The localization of monoamine oxidase in the mitochondrial outer membrane was studied in preparations of human liver mitochondrial and brain-cortex non-synaptosomal and synaptosomal mitochondria. 2. Immunochemical accessibility in iso-osmotic and hypo-osmotic mitochondrial preparations was used to localize the enzyme. 3. It was shown that the immunochemically accessible tyramine-oxidizing activity was distributed approximately equally on both surfaces of the membrane in human liver and brain-cortex non-synaptosomal mitochondria. However, the immunochemically accessible beta-phenethylamine-oxidizing activity was situated predominantly on the outer surface, and the immunochemically accessible 5-hydroxytryptamine-oxidizing activity was situated predominantly on the inner surface of the mitochondrial outer membrane in liver and brain-cortex non-synaptosomal mitochondrial preparations. 4. Considerable variation in the distribution of the enzyme in preparations of synaptosomal mitochondria was seen. 5. The simplest model consistent with our observations is that, in liver and brain-cortex non-synaptosomal mitochondria, the tyramine-oxidizing activity is distributed on both sides of the mitochondrial outer membrane, the beta-phenethylamine-oxidizing activity is located on the outer surface of the outer membrane and the 5-hydroxytryptamine-oxidizing activity is located on the inner surface of the mitochondria outer membrane.

Aged↗
PubMed1979

Immunochemical characterization of monoamine oxidase from human liver, placenta, platelets and brain cortex.

1. Antiserum raised to purified human liver monoamine oxidase was used to characterize the monoamine oxidase from human liver, brain cortex, placenta and platelets. 2. Antibodies to monoamine oxidase were purified by adsorption with a mitochondrial preparation. 3. Monoamine oxidase was present in liver particle-free supernatant as measured by enzyme activity and immunodiffusion. 4. Multiple precipitin lines were obtained on immunodiffusion analysis against the purified liver enzyme. It is proposed that this is due to either aggregation or to differential lipid binding. 5. The results suggest that the functionally different enzymes found in liver, brain cortex, platelets and placenta are immunochemically related and may be identical.

Antigens↗
PubMed1975

Antibody-hapten interactions in vivo in mice and sheep.

From 5 min to 5 h after an intravenous injection of one of the haptens, elipson-dinitrophenyl-lysine, 2,4-dinitrophenol (DNP), or procaine, mice that were actively immunised against these haptens held more of the hapten in their plasma than did normal mice. Over the same time interval, mice that had been passively immunised with sheep anti-procaine antisera and then treated with procaine held more procaine in their plasma than did mice treated with normal sheep serum. When procaine or DNP was administered orally or intraperitoneally to sheep with circulating antibody to the hapten, the antibody titre was usually reduced 1 h after dosing but returned to the pre-dosing titre by 24 h. Experiments indicated that the reduction in antibody titre was due to in vivo neutralisation of antibody by the hapten.

Animals↗