Purification and characterization of 3-dehydroquinase from Escherichia coli.

A procedure has been developed for the purification of 3-dehydroquinase from Escherichia coli. Homogeneous enzyme with specific activity 163 units/mg of protein was obtained in 19% overall yield. The subunit Mr estimated from polyacrylamide-gel electrophoresis in the presence of sodium dodecyl sulphate was 29,000. The native Mr, estimated by gel permeation chromatography on Sephacryl S-200 (superfine) and on TSK G3000SW, was in the range 52,000-58,000, indicating that the enzyme is dimeric. The catalytic properties of the enzyme have been determined and shown to be very similar to those of the biosynthetic 3-dehydroquinase component of the arom multifunctional enzyme of Neurospora crassa.     

kDNA minicircles of the major sequence class of C. fasciculata contain a single region of bent helix widely separated from the two origins of replication

The major sequence class of Crithidia fasciculata minicircles is shown to have a single region of bent helical DNA widely separated from the two replication origins located 180 degrees apart on the minicircle map. The position of the bend in the DNA has been mapped both by gel electrophoretic methods and by direct electron microscopic observation of the DNA. This sequence directed bending is apparently the result of homopolymeric dA X dT tracts 4-6 base pairs long repeated in phase with the helix screw. The region of the bend contains nineteen such homopolymeric tracts in a region of about 200 base pairs with sixteen of the tracts oriented in the same direction.     

Sequencing and identification of a cDNA clone for tomato polygalacturonase.

The 2a isoenzyme of tomato polygalacturonase was purified from ripe fruit and characterised. The N-terminal amino acid sequence of the protein was determined in order to identify polygalacturonase cDNA clones. The nucleotide sequence of a ripening-related cDNA (pTOM 6) was determined and found to encode the N-terminal sequence of mature polygalacturonase 2a. The complete open reading frame encodes a polypeptide of molecular weight 50,051, including a putative pre-sequence of 71 amino acids.     

Studies on Inc-P plasmids in Erwinia carotovora subsp. carotovora

Abstract Inc-P plasmids, RP4, R751, pMO850, and pRK2013 were transferred to Erwinia carotovora . These plasmids were stably maintained in E. carotovora and the transconjugants were efficient donors of respective plasmids to other strains of E. carotovora and Escherichia coli . These plasmids were not able to mobilize chromosomal markers from one strain of E. carotovora to another strain of E. carotovora even in the presence of homologous DNA sequences on the plasmid and the bacterial chromosome. The presence of Inc-P plasmid does not affect the pathogenic phenotype of E. carotovora . A broad host range Inc-P cosmid, pLAFR1, was transferred to E. carotovora with the help of pRK2013, suggesting the potential use of a binary plasmid system for genetic complementation in E. carotovora .     

Nitrogen Source Regulates Glutamate Dehydrogenase NADP Synthesis in Neurospora crassa

Neurospora crassa glutamate dehydrogenase-NADP (EC 1.3.1.3) has a higher activity when mycelium is grown on ammonium or nitrate as nitrogen source than when grown on glutamate or glutamine. Quantitative immunoelectrophoresis established that, under all conditions, enzyme activity corresponded to enzyme concentration. Isotope incorporation studies demonstrated that the nitrogen source exerts its regulation at the level of de novo enzyme synthesis.     

Role of ions in activation of human lymphocytes

Phytohemagglutinin (PHA)-stimulated lymphocytes were cultured in media containing varying levels of K+, Mg2+, Ca2+. Cell activation was monitored by measuring nuclear diameter and by evaluating the area of nucleolus which reacted with silver nitrate. Decreasing extracellular K+ from normal levels (5.0 mM) to 14% (0.7 mM) and decreasing extracellular Mg2+ from normal levels (1.0 mM) to 14% (0.14 mM) did not affect nuclear diameter or silver nitrate reactivity of PHA-stimulated lymphocytes. Chelation of extracellular Ca2+ with EGTA during the first 24 h after PHA stimulation completely inhibited the increases in silver reactivity and nuclear diameter associated with stimulation. Chelation of extracellular Ca2+ 48 h after PHA stimulation did not inhibit lymphocyte stimulation. Inhibitory effects of EGTA were completely reversed if CaCl2 was added to the medium within 24 h of PHA stimulation. By 48 h the effects were irreversible.     

Isolation and sequence of a non-opioid peptide derived from proenkephalin

A non-opioid peptide derived from adrenal proenkephalin has been isolated and sequenced. The sequence of this peptide is Ser-Pro-His-Leu-Glu-Asp-Glu-Thr-Lys-Glu-Leu-Gln (Proenkephalin 168-180). This sequence represents the portion of Peptide I that is cleaved to yield Peptide E. This peptide is processed in a similar manner to the opioid peptides and is present at approximately the same level as Peptide E.