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51.
Evidence is presented that although many proteins from the fronds of Lemna minor L. undergo enhanced degradation during osmotic stress, ribulose-1,5-bisphosphate carboxylase (RuBPCase) is not degraded. Instead RuBPCase is converted in a series of steps to a very high-molecular-weight form. The first step involves the induction of an oxidase system which after 24 h of stress converts RuBPCase to an acidic and catalytically inactive form. Subsequently, the oxidised RuBPCase protein is gradually polymerized to a number of very large aggregates (molecular weight of several million).The conversion of RuBPCase to a high-molecular-weight form appears to be correlated with (i) a reduction in the number of-SH residues and (ii) the susceptibility to in-vitro proteolysis. Indeed, the number of-SH groups per RuBPCase molecule decreases from 89 in the native enzyme to 54 and 22 in the oxidised and polymerized forms, respectively. On the other hand, the oxidised enzyme is more susceptible to in-vitro proteolysis than the native form. However, it is the polymerized form of RuBPCase which is particularly susceptible to in-vitro proteolysis.Western-blotting experiments and anti-ubiquitin antibodies were used to detect the presence of ubiquitin conjugates in extracts from osmotically stressed Lemna fronds. The possible involvement of ubiquitin in the formation of the aggregates is discussed.Abbreviations DTT
dithiothreitol
- EDTA
ethylenediamine-tetraacetic acid
- FPLC
fast protein liquid chromatography
- kDa
kilodaltons
- PAGE
polyacrylamide gel electrophoresis
- PMSF
phenylmethylsulphonyl fluoride
- RuBPCase
ribulose bisphosphate carboxylase
- SDS
sodium dodecyl sulphate
- Tris
2-amino-2-(hydroxymethyl)-1,3-propanediol 相似文献
52.
L. O. e Silva S. P. Singh M. A. Pastor-Corrales 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1989,78(5):619-624
Summary Inheritance of resistance to common bacterial blight in the trifoliate leaf, plant canopy, and pods was controlled by a single major gene. Additive followed by dominance effects were more important than epistatic interactions. Narrow-sense heritability values ranged from 0.18 to 0.87 for trifoliate leaf, from 0.26 to 0.76 for canopy, and from 0.11 to 0.36 for pods. Observed gains from selection for resistance were higher than expected gains. Implications of these results in breeding for resistance are discussed. 相似文献
53.
T L Machado L C Formiga R D Machado R R da Silva 《Memórias do Instituto Oswaldo Cruz》1989,84(2):241-243
The isolation of toxigenic Corynebacterium diphtheriae from sperm is reported. The organism was identified through the investigation of fluorescence under the UV light, the presence of pirazinecarboxilamidase enzyme (Pyz), in vitro and in vivo and virulence methods (single radial immunodiffusion, cell culture, guinea pig intradermic test). The strain was initially considered nontoxinogenic by single radial immunodiffusion, but its virulence was observed afterwards, when we applied the tests already mentioned. The strain could be considered a "Diphtheroid" without adequate specification. 相似文献
54.
55.
C. E. Scanlon N. R. Chalmers M. A. O. Monteiro da Cruz 《International journal of primatology》1989,10(2):123-136
Three wild groups of common marmoset, Callithrix jacchus jacchus,in north-east Brazil, of approximately similar size, had home ranges between 2.5 and 6.5 ha. But their core areas were similar
in size between 1.0 and 1.5 ha, with a monthly area of heavy use between 1.1 and 1.6 ha. The groups were selective in the
use of their home ranges, even though they were small: they used some areas heavily and others lightly. The core areas had
higher densities of trees that produced gum exudates than did other parts of the home ranges. Our data suggest that a group
of marmosets in this habitat may require a minimum of about 50 gum trees in its home range at a minimum density of about 50
trees/ha. In addition, the animals require suitable trees in which to sleep. We suggest that patches of forest with these
desirable properties remain relatively fixed in size and location over the years and that individual animals are constantly
in flux between them. 相似文献
56.
L R Chen C J Yuan G Somasekhar P Wejksnora J E Peterson A M Myers L Graves P T Cohen E F da Cruz e Silva D J Graves 《Biochemical and biophysical research communications》1989,161(2):746-753
A cDNA encoding the entire tau subunit of rabbit skeletal muscle phosphorylase kinase was reconstructed and inserted into a plasmid containing the Escherichia coli ptac promoter and a constructed plasmid containing the ptac promoter and bacterial chloramphenicol acetyl transferase (CAT) gene, respectively. A significant phosphorylase kinase activity was found, in the first case. In the second case, a fused protein containing 73 amino acids from the CAT protein was obtained. After renaturation, the CAT-tau subunit protein shows enzymatic activity similar to the HPLC-purified and renatured tau subunit. 相似文献
57.
Pedro J. N. Silva Richard K. Koehn Walter J. Diehl III Robin P. Ertl Elaine B. Winshell Mauro Santos 《Biochemical genetics》1989,27(7-8):451-467
Four samples of the musselMytilus edulis were taken between 1984 and 1987 from Stony Brook, New York, and used to study the glucose-6-phosphate isomerase (GPI) polymorphism
in this species.In vitro specific activity andin vivo flux measured in the same animals were found to be significantly correlated. A significant effect of GPI genotype on flux
was observed in one of the samples; overall, significant evidence of effect of genotype on enzyme activity was also obtained.
GPI activities of common genotypes tend to deviate less from the population mean than those of rare (frequency less than 5%)
genotypes. This suggests the possibility that rare GPI genotypes are rare as a consequence of having biochemical properties
that deviate from an optimum level and, therefore, having a lower fitness. In support of this hypothesis, we found in one
of our samples that shell length is a concave function of GPI activity with an intermediate optimum activity level.
The financial support provided to P.J.N.S. by the Luso-American Educational Commission (Fulbright Program), the Instituto
Nacional de Investigacao Científica (Portugal), and the Faculdade de Ciências da Universidade de Lisboa during several stages
of this research is gratefully acknowledged. Financial support from the Ministerio de Educatión y Ciencia (Spain) in the form
of a postdoctoral Fulbright/MEC fellowship to M.S. is also gratefully acknowledged. Research was supported by National Science
Foundation Grant BSR-8415060 to R.K.K. This is contribution No. 736 from the Program in Ecology and Evolution, State University
of New York at Stony Brook.
On leave from Departamento de Biologia Vegetal, Faculdade de Ciências, Universidade de Lisboa, Campo Grande C2, Lisboa, Portugal. 相似文献
58.
The major type-1 protein phosphatase catalytic subunits are the same gene products in rabbit skeletal muscle and rabbit liver 总被引:3,自引:0,他引:3
P T Cohen D L Schelling O B da Cruz e Silva H M Barker P Cohen 《Biochimica et biophysica acta》1989,1008(1):125-128
The catalytic subunit of protein phosphatase-1 (PP1) isolated from rabbit liver had the same electrophoretic mobility as, and yielded peptide maps identical to those of the 33 kDa form of rabbit skeletal muscle PP1. The predicted amino-acid sequences of PP1 obtained from three rabbit liver cDNA clones were identical to that of PP1 alpha from rabbit skeletal muscle. These findings suggest that the distinctive substrate specificities and regulatory properties of hepatic and skeletal muscle type-1 protein phosphatases are not conferred by the catalytic subunits themselves, but by regulatory subunits that are complexed to the catalytic subunits in vivo. 相似文献
59.
60.
Patrick Ferreira 《CMAJ》1990,143(12):1336-1337