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1.
A Jukkola J Risteli L Risteli 《Biochemical and biophysical research communications》1990,170(1):264-269
Sodium chlorate, a potent inhibitor of sulfation reactions, completely inhibits the formation of tyrosine-o-sulfate in type III procollagen in human fibroblasts, when used in concentrations that do not affect the incorporation of radioactive amino acids into protein. The unsulfated type III procollagen is secreted into the medium at a rate comparable, to those of sulfated type III procollagen and type I procollagen, which normally does not undergo sulfation. The enzymatic cleavage of the aminoterminal propeptide of type III procollagen is incomplete in fibroblast cultures, irrespective of the sulfation status of the protein. 相似文献
2.
Significance of Polyamines for Flowering in Spirodela punctata 总被引:1,自引:0,他引:1
Spirodela punctata strain O 5, a quantitative long-day plant,flowers only when ethylene-diamine-di-o-hydroxyphenylaceticacid (EDDHA) or salicylic acid was added to the nutrient medium[Scharfetter et al. (1978) Z. Pflanzenphysiol. 87: 445]. Undersuch conditions, cyclohexylamine and methylglyoxal-bis(guanylhydrazone)(both blockers of polyamine synthesis) inhibited flowering withoutsignificant effects on vegetative growth. Supply of spermidineabolished completely the inhibitor effects, but cannot replacethe EDDHA effect on flowering.
1Dedicated to Prof. O. H. Volk, Wurzburg, on his 85th birthday.
2Present address: Facultad de Ciencias Forestales, UniversidadAutónoma de Nuevo León. Ap. Post. 41, 67700 Linares,Nuevo León, México. (Received October 19, 1988; Accepted February 3, 1989) 相似文献
3.
Influence of maize root mucilage on soil aggregate stability 总被引:9,自引:0,他引:9
This study was undertaken to determine the effects of root exudates on soil aggregate stability. Root mucilage was collected
from two-month old maize plants (Zea mays L.) Mucilage and glucose solutions were added at a rate of 2.45 g C kg−1 dry soil to silty clay and silt loam soils. Amended soils, placed in serum flasks, were incubated for 42 d with a drying-wetting
cycle after 21 d. Evolved CO2 was measured periodically as well as the water-stable aggregates and soluble sugar and polysaccharide content of the soil.
In mucilage-amended soils CO2 evolution started with a lag phase of 2–3 days, which was not observed in glucose-amended soils. There was then a sharp increase
in evolved CO2 up to day 7. During the second incubation period there were only small differences in evolved C between treatments. Incorporation
of mucilage in both soils resulted in a spectacular and immediate increase in soil aggregate stability. Thereafter, the percent
of water-stable aggregates quickly decreased parallel to microbial degradation. On completion of the incubation, aggregate
stability in the silty clay soil was still significantly higher in the presence of mucilage than in the control. This work
supports the assumption that freshly released mucilage is able to stick very rapidly to soil particles and may protect the
newly formed aggregates against water destruction. On the silty clay, microbial activity contributes to a stabilization of
these established organo-mineral bounds. 相似文献
4.
Structural diversity and domain composition of a unique collagenous fragment (intima collagen) obtained from human placenta. 总被引:23,自引:3,他引:20
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Intima collagen was obtained from pepsin digests of human placenta in two forms, which differ to some extent in the size of their constituent polypeptide chains (Mr 50 000-70 000). These chains are connected by disulphide bonds to large aggregates. The aggregates are arranged in a triple-helical conformation with a remarkably high thermal stability (Tm 41-62 degrees C) and are resistant to further proteolytic digestion. Reduction of as little as 5% of the disulphide bonds produces mainly monomeric triple helices (Mr about 160 000) with Tm 32 degrees C. Partially reduced material can be separated into triple-helical and non-collagenous domains by proteolysis. Pepsin releases a collagenous component with chains of Mr 38 000. Bacterial collagenase liberates two non-collagenous segments (Mr 15 000-30 000) rich in cystine. Treatment with collagenase before reduction separates intima collagen into a large fragment composed of collagenous (Tm 41 degrees C) and non-collagenous structures and a single non-collagenous segment. The data support the electron-microscopical model of intima collagen [Furthmayr, Wiedemann, Timpl, Odermatt & Engel (1983) Biochem. J. 211, 303-311], indicating that the basic unit of the fragment consists of a continuous triple helix joining two globular domains. 相似文献
5.
6.
The formation of 3-hydroxyproline was studied with crude rat kidney cortex extract as a source of enzyme and chick embryo tendon protocollagen and procollagen or cartilage protocollagen as a substrate. Synthesis of 3-hydroxyproline was observed with all these substrates and the formation of 3-hydroxyproline ranged up to seven residues per pro-alpha-chain. The highest rate of 3-hydroxylation took place at 20 degrees C and the reaction required Fe2+, O2,2-oxoglutarate and ascorbate. The formation of 3-hydroxyproline was affected by chain length and the conformation of the substrate, in that longer polypeptide chains proved better substrates, while the native triple-helical conformation of protocollagen or procollagen completely prevented the reaction. Formation of 3-hydroxyproline with tendon procollagen as a substrate was not inhibited by antiserum to prolyl 4-hydroxylase or by poly(L-proline) when these substances were used in concentrations which clearly inhibited 4-hydroxyproline formation with tendon protocollagen as a substrate. Furthermore, pure prolyl 4-hydroxylase did not synthesize any 3-hydroxyproline under conditions in which the crude rat kidney cortex enzyme would readily do so. The data thus strongly suggest that prolyl 3-hydroxylase and prolyl 4-hydroxylase are separate enzymes. 相似文献
7.
Immunochemical distinction between two different chains of type IV collagen. 总被引:2,自引:0,他引:2
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Antisera against mouse and human basement-membrane type IV collagen showed in radioimmunoassays distinct binding with large pepsin fragments obtained from the C-terminal portions of alpha 1 (IV)- and alpha 2 (IV)-chains. These reactions were specific for each constituent polypeptide chain. The data were confirmed by immunoadsorption, allowing the separation of antibodies with restricted chain specificity. Inhibition assays with CNBr peptides demonstrated the different localizations of antigenic determinants, which were either species-specific or shared by the human and mouse antigens. 相似文献
8.
Radioimmunoassays were developed for the basement membrane components, 7 S collagen and fragments of the noncollagenous protein laminin, which allowed quantitative analysis of as little as 0.1–0.4 ng of these proteins. Similar materials could be detected by these assays in serum, in kidney digests, and in the medium of cell cultures obtained from mice and rats. Distinct changes in the amounts of antigen in serum and kidney were observed during aging and in mice inoculated with a basement membrane tumor. 相似文献
9.
Macromolecular structure of basement membrane collagens 总被引:22,自引:0,他引:22
K Kühn H Wiedemann R Timpl J Risteli H Dieringer T Voss R W Glanville 《FEBS letters》1981,125(1):123-128
10.