Identification, purification, and characterization of phosphotyrosine-specific protein phosphatases from cultured chicken embryo fibroblasts.

Tyrosine phosphorylation catalyzed by a unique class of protein kinases is an important process in both normal cell proliferation and oncogenic transformation. In this study, phosphoprotein phosphatases specific for the dephosphorylation of phosphotyrosine residues were partially purified from secondary chicken embryo fibroblasts, using 32P-labeled immunoglobulin G phosphorylated by pp60src as substrate. Crude cell extracts contained ca. 70% of the activity in the soluble form and ca. 30% associated with a crude membrane fraction. The soluble activity was purified by using DEAE-cellulose and carboxymethyl cellulose column chromatography and gel filtration, and at least three enzyme species of apparent Mr 55,000 (pTPI), 50,000 (pTPII), and 95,000 (pTPIII)--comprising ca. 20, 45, and 35%, respectively, of the total activity--were resolved. All three enzymes possessed somewhat similar properties. They had a pH optimum of about 7.4, they were inhibited by Zn2+, vanadate, ATP, and ADP, and they were unaffected by divalent metal cations, EDTA, and F- under standard assay conditions employing a physiological ionic strength. These properties suggest that they represent a class of enzymes distinct from well-known phosphoseryl-phosphothreonyl-protein phosphatases and that dephosphorylation of phosphotyrosine-containing proteins may be carried out by a unique family of phosphoprotein phosphatases. Transformation by Rous sarcoma virus resulted in a small increase in phosphotyrosyl-protein phosphatase activity.     

Apport de la biochimie flavonique à la systematique du genre Lycopodium

A systematic study of Lycopodium s.l. shows that only flavones occur in the four genera Huperzia, Lepidotis, Lycopodium s.s. and Diphasium. The arrangement of these taxa is discussed on the basis of the distribution of tricin, selgin, chrysoeriol, luteolin and apigenin. The evolutionary significance of these results and the uniqueness of Lycopodium phenolic metabolism are outlined.     

Chrysonila sitophila (TFB-27441): A hyperlignolytic strain

Summary C. sitophila strain TFB-27441 showed 2–3 times higher lignolytic activity thanPhanerochaete chrysosporium (BKM-F-1767 strain). Lignin had a marked effect on the ligninase activity indicating that some induction or activation mechanism is involved in lignin degradation byC. sitophila.     

Coprecipitation modulates the solubility of minerals in bovine milk

The solubilities of zinc, iron, copper, magnesium, calcium, inorganic phosphate, and citrate in milk decreased when acidic milk preparations were neutralized. In decaseinated bovine milk soluble zinc, iron, and copper were reduced 90%, 60%, and 50%, respectively, as the pH was raised from 4 to 7. Simultaneous precipitation of minerals and citrate was confirmed by analysis of washed precipitate. We propose that the diminished solubilities of zinc, iron, copper, magnesium, and citrate are linked to the precipitation of calcium phosphate through one or more mechanisms of coprecipitation. Such control on mineral solubility may have an impact upon mineral absorption from milk.     

Polyploidy and habitat differentiation in Dactylis glomerata L. from Galicia (Spain)

Summary The microdistribution of diploid and tetraploid plants of Dactylis glomerata L. was examined and related to their immediate environment in several sites in central Galicia, where morphologically indistinguishable individuals of both ploidies grow in sympatry. The two related cytotypes differed in habitat preference. Diploids were mainly confined to the low-density forest-floor habitat in woodlands of mostly ancient origin, whereas tetraploids were widespread in varied habitats but clearly predominant in open areas, particularly in disturbed anthropic sites. The in situ comparison of plant performance showed that where plants of each ploidy were more common they produced more tillers, panicles and seeds. This habitat preference closely reflected differences in life-history characteristics. The tetraploids had an early and short flowering time almost always completed before the aestival drought, whereas the diploids began to flower several weeks later and flowered throughout the drought. Comparisons along artificial gradients of soil water availability and light transmittance indicated that the cytotypes had distinct physiological requirements which probably originated in metabolic and more general genetic differentiation and could be directly attributable to ploidy. Habitat differentiation increases the species' colonizing ability. It also amplifies divergence in reproductive strategy between diploids and tetraploids, which reduces ineffective crossing between cytotypes and thereby permits them to coexist in sympatry. The effect of hybridization at the polyploid level on the differentiation between cytotypes was assessed from the recent introduction of a foreign tetraploid entity into the study area. Hybridization between the two distinct tetraploids was found to increase habitat differentiation between the diploids and the tetraploids, but the major part of this differentiation is probably attributable to ploidy itself.     

Cloning of the cysB gene of Erwinia carotovora subsp. carotovora, and the identification of its product

Summary The suicide vector pJB4JI was used to generate a range of Tn5-induced mutants of Erwinia carotovora subsp. carotovora (Ecc). One mutant, HC500, was a cysteine auxotroph which had a non-pectolytic, non-cellulolytic, non-proteolytic phenotype when grown under sulphate-limitation. The cysteine lesion of HC500 was shown to be analogous to the cysB mutation of Escherichia coli. The Ecc-cysB ⁺ gene product was identified as a protein of M_r 36000.     

Structure and expression of the overlapping ND4L and ND5 genes of Neurospora crassa mitochondria

Summary Genes homologous to the mammalian mitochondrial NADH dehydrogenase subunit genes ND4L and ND5 were identified in the mitochondrial genome of the filamentous fungus Neurospora crassa, and the structure and expression of these genes was examined. The ND4L gene (interrupted by one intervening sequence) potentially encodes an 89 residue long hydrophobic protein that shares about 26% homology (or 41% homology if conservative amino acid substitutions are allowed) with the analogous human mitochondrial protein. The ND5 gene (which contains two introns) encodes a 715 residue polypeptide that shares 23% homology with the human analogue; a 300 amino acid long region is highly conserved (50% homology) in the two ND5 proteins. The stop codon of the ND4L gene overlaps the initiation codon of the downstream ND5 gene, and the two genes are contranscribed and probably cotranslated. A presumed mature dicistronic (ND4L plus ND5) RNA was detected. The postulated mRNA (about 3.2 kb) contains 5 and 3 non-coding regions of about 86 and 730 nucleotides, respectively; this species is generated from very large precursor RNAs by a complex processing pathway. The ND4L and ND5 introns are all stable after their excision from the precursor species.Abbreviations bp base pairs - rRNA ribosomal RNA - ND NADH dehydrogenase - URF unidentified reading frame - kDal kilodaltons; a.a., amino acid