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1.
D Ashford R A Dwek J K Welply S Amatayakul S W Homans H Lis G N Taylor N Sharon T W Rademacher 《European journal of biochemistry》1987,166(2):311-320
The carbohydrate moieties of Erythrina cristagalli lectin were released as oligosaccharides by hydrazinolysis, followed by N-acetylation and reduction with NaB3H4. Fractionation of the tritium-labelled oligosaccharide mixture by Bio-Gel P-4 column chromatography and high-voltage borate electrophoresis revealed that it is composed of five neutral oligosaccharides. Structural studies by sequential exoglycosidase digestion in combination with methylation analysis and two-dimensional 1H-NMR showed that the major component was the fucose-containing heptasaccharide Man alpha 3(Man alpha 6)(Xyl beta 2)Man beta 4GlcNAc beta 4(Fuc alpha 3)GlcNAcol. This is the first report of such a structure in plant lectins. Small amounts of the corresponding afucosyl hexasaccharide were also identified, as well as three other minor components. The structure of the heptasaccharide shows the twin characteristics of a newly established family of N-linked glycans, found to date only in plants. The characteristics are substitution of the common pentasaccharide core [Man alpha 3(Man alpha 6)Man beta 4GlcNAc beta 4GlcNAc] by a D-xylose residue linked beta 1----2 to the beta-mannosyl residue and an L-fucose residue linked alpha 1----3 to the reducing terminal N-acetylglucosamine residue. The oligosaccharide heterogeneity pattern for Erythrina cristagalli lectin was also found for the lectins from four other Erythrina species and the lectins of two other legumes, Sophora japonica and Lonchocarpus capassa. 相似文献
2.
The methionine-rich domain of the 54 kDa subunit of signal recognition particle is sufficient for the interaction with signal sequences. 总被引:10,自引:1,他引:9
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The signal recognition particle (SRP) binds to signal sequences when they emerge from a translating ribosome and targets the complex of ribosome, nascent chain and SRP to the membrane of the rough endoplasmic reticulum (rER) allowing the co-translational translocation of the nascent chain. By photo-crosslinking it has been shown that the signal sequence of preprolactin (PPL) only interacts with the methionine-rich (M) domain of the 54 kDa protein subunit (SRP54) of SRP. Here we show that (i) a signal-anchor sequence is likewise crosslinked only to the methionine-rich domain of SRP54, (ii) free SRP54 can interact with signal sequences independently of the other components of SRP, (iii) its M domain suffices to perform this function, and (iv) an essentially intact M domain is required for signal sequence recognition. Alkylation of the N+G domain in intact SRP54 with N-ethyl maleimide (NEM), but not after cleavage with V8 protease, prevents the binding of a signal sequence to the M domain. This suggests a proximity between the N+G and M domains of SRP54 and raises the possibility that the role of the N+G domain may be to regulate the binding and/or the release of signal sequences. 相似文献
3.
Summary The ectomycorrhizal fungus,Paxillus involutus, produces sclerotia in culture. These can be induced to form on agar medium by exposing mycelium grown at 25°C to various temperatures between6°C and 15°C. Sclerotia formed at 10°C and above were large and covered with drops of exudate, while those formed at 6°C or 8°C were very small and did not produce an exudate. Mature sclerotia were bounded by a compact rind and contained abundant storage reserves. Histochemistry of the larger sclerotia showed large quantities of protein stored as protein bodies in the cytoplasm, lipid present as small droplets, glycogen granules stored in the cytoplasm and polyphosphate present as small granules in the cytoplasm and in the protein bodies. Energy dispersive X-ray microanalysis confirmed the presence of phosphate in the granules and was used to map its distribution throughout the sclerotium. The smaller sclerotia induced at 8°C and below on the same medium had the same basic structure and composition, but lacked the complex phenolic cell network found in large sclerotia, and had abundant extracellular polysaccharides. The rind was not well developed and these small sclerotia are interpreted to have been arrested at an early stage of development. 相似文献
4.
Hardies SC; Martin SL; Voliva CF; Hutchison CA d; Edgell MH 《Molecular biology and evolution》1986,3(2):109-125
5.
A major difference between the divergence patterns within the lines-1 families in mice and voles 总被引:3,自引:0,他引:3
Vanlerberghe F; Bonhomme F; Hutchison CA d; Edgell MH 《Molecular biology and evolution》1993,10(4):719-731
L1 retroposons are represented in mice by subfamilies of interspersed
sequences of varied abundance. Previous analyses have indicated that
subfamilies are generated by duplicative transposition of a small number of
members of the L1 family, the progeny of which then become a major
component of the murine L1 population, and are not due to any active
processes generating homology within preexisting groups of elements in a
particular species. In mice, more than a third of the L1 elements belong to
a clade that became active approximately 5 Mya and whose elements are >
or = 95% identical. We have collected sequence information from 13 L1
elements isolated from two species of voles (Rodentia: Microtinae: Microtus
and Arvicola) and have found that divergence within the vole L1 population
is quite different from that in mice, in that there is no abundant
subfamily of homologous elements. Individual L1 elements from voles are
very divergent from one another and belong to a clade that began a period
of elevated duplicative transposition approximately 13 Mya. Sequence
analyses of portions of these divergent L1 elements (approximately 250 bp
each) gave no evidence for concerted evolution having acted on the vole L1
elements since the split of the two vole lineages approximately 3.5 Mya;
that is, the observed interspecific divergence (6.7%-24.7%) is not larger
than the intraspecific divergence (7.9%-27.2%), and phylogenetic analyses
showed no clustering into Arvicola and Microtus clades.
相似文献
6.
7.
Molecular phylogeny and divergence times of drosophilid species 总被引:32,自引:15,他引:17
The phylogenetic relationships and divergence times of 39 drosophilid
species were studied by using the coding region of the Adh gene. Four
genera--Scaptodrosophila, Zaprionus, Drosophila, and Scaptomyza (from
Hawaii)--and three Drosophila subgenera--Drosophila, Engiscaptomyza, and
Sophophora--were included. After conducting statistical analyses of the
nucleotide sequences of the Adh, Adhr (Adh-related gene), and nuclear rRNA
genes and a 905-bp segment of mitochondrial DNA, we used Scaptodrosophila
as the outgroup. The phylogenetic tree obtained showed that the first major
division of drosophilid species occurs between subgenus Sophophora (genus
Drosophila) and the group including subgenera Drosophila and Engiscaptomyza
plus the genera Zaprionus and Scaptomyza. Subgenus Sophophora is then
divided into D. willistoni and the clade of D. obscura and D. melanogaster
species groups. In the other major drosophilid group, Zaprionus first
separates from the other species, and then D. immigrans leaves the
remaining group of species. This remaining group then splits into the D.
repleta group and the Hawaiian drosophilid cluster (Hawaiian Drosophila,
Engiscaptomyza, and Scaptomyza). Engiscaptomyza and Scaptomyza are tightly
clustered. Each of the D. repleta, D. obscura, and D. melanogaster groups
is monophyletic. The splitting of subgenera Drosophila and Sophophora
apparently occurred about 40 Mya, whereas the D. repleta group and the
Hawaiian drosophilid cluster separated about 32 Mya. By contrast, the
splitting of Engiscaptomyza and Scaptomyza occurred only about 11 Mya,
suggesting that Scaptomyza experienced a rapid morphological evolution. The
D. obscura and D. melanogaster groups apparently diverged about 25 Mya.
Many of the D. repleta group species studied here have two functional Adh
genes (Adh-1 and Adh-2), and these duplicated genes can be explained by two
duplication events.
相似文献
8.
David Ashford Rajeev Menon Anthony K. Allen Albert Neuberger 《The Biochemical journal》1981,199(2):399-408
1. Modification of potato (Solanum tuberosum) lectin with acetic anhydride blocked 5.1 amino and 2.7 tyrosyl groups per molecule of lectin and decreased the haemagglutinating activity of the lectin. De-O-acetylation regenerated 2.0 of the tyrosyl groups and resulted in a recovery of activity. 2. Modification with citraconic anhydride or cyclohexane-1,2-dione did not greatly affect activity, although modification of amino and arginyl groups could be demonstrated. 3. Treatment with tetranitromethane nitrated 3.7 tyrosine residues per molecule of lectin with concomitant loss of activity. The presence of 0.1m-NN′N″-triacetylchitotriose (a potent inhibitor of the lectin) in the reaction medium protected all the tyrosyl residues from nitration and the lectin was fully active. 4. Modification of tryptophyl groups with 2-hydroxy-5-nitrobenzyl bromide and 2,3-dioxoindoline-5-sulphonic acid modified 0.9 and 2.6 residues per molecule of lectin respectively with a loss of activity in each case. Reaction of potato lectin with 2,3-dioxoindoline-5-sulphonic acid in the presence of inhibitor protected 2.4 residues of tryptophan from the reagent. Loss of haemagglutination activity was prevented under these conditions. 5. Reaction of carboxy groups, activated with carbodi-imide, with α-aminobutyric acid methyl ester led to the incorporation of 5.3 residues of the ester per molecule of lectin. Presence of inhibitor in this case, although protecting activity, did not prevent modification of carboxy groups; in fact an increase in the number of modified residues was seen. This effect could be imitated by performing the reaction in 8m-urea. In both cases the number of carboxy groups modified was close to the total number of free carboxy groups as determined by the method of Hoare & Koshland [(1967) J. Biol. Chem. 242, 2447–2453]. Guanidination of lysine residues after carboxy-group modification gave less homoarginine than did the unmodified lectin under the same conditions, suggesting the formation of intramolecular cross-links during carbodi-imide activation. 6. It is suggested from the results presented that amino, arginyl, methionyl, histidyl and carboxyl groups are not involved in the activity of the lectin and that tyrosyl and tryptophyl groups are very closely involved. These findings are similar to those reported for other proteins that bind N-acetylglucosamine oligomers and also fit the general trend in other lectins. 相似文献
9.
Sulfate reduction and S-oxidation in a moorland pool sediment 总被引:3,自引:2,他引:1
In an oligotrophic moorland pool in The Netherlands, S cycling near the sediment/water boundary was investigated by measuring (1) SO4
2– reduction rates in the sediment, (2) depletion of SO4
2– in the overlying water column and (3) release of35S from the sediment into the water column. Two locations differing in sediment type (highly organic and sandy) were compared, with respect to reduction rates and depletion of SO4
2– in the overlying water.Sulfate reduction rates in sediments of an oligotrophic moorland pool were estimated by diagenetic modelling and whole core35SO4
2– injection. Rates of SO4
2– consumption in the overlying water were estimated by changes in SO4
2– concentration over time in in situ enclosures. Reduction rates ranged from 0.27–11.2 mmol m–2 d–1. Rates of SO4
2– uptake from the enclosed water column varied from –0.5, –0.3 mmol m–2 d–1 (November) to 0.43–1.81 mmol m–2 d–1 (July, August and April). Maximum rates of oxidation to SO4
2– in July 1990 estimated by combination of SO4
2– reduction rates and rates of in situ SO4
2– uptake in the enclosed water column were 10.3 and 10.5 mmol m–2 d–1 at an organic rich and at a sandy site respectively.Experiments with35S2– and35SO4
2– tracer suggested (1) a rapid formation of organically bound S from dissimilatory reduced SO4
2– and (2) the presence of mainly non SO4
2–-S derived from reduced S transported from the sediment into the overlying water. A35S2– tracer experiment showed that about 7% of35S2– injected at 1 cm depth in a sediment core was recovered in the overlying water column.Sulfate reduction rates in sediments with higher volumetric mass fraction of organic matter did not significantly differ from those in sediments with a lower mass fraction of organic matter.Corresponding author 相似文献