Exoglucanase (exo-1,3-β-D-glucan glycohydrolase, EC 3.2.1.56) activity secreted by Saccharomyces cerevisiae into the culture medium was separated by ion exchange chromatography into two glycoprotein isoenzymes which contributed 10%
(exoglucanase I) and 90% (exoglucanase II) towards the total activity. Analysis of the “in vitro” deglycosylated products
by polyacrylamide gel electrophoresis under native or denaturing conditions indicated that the protein portions of both exoglucanases
exhibited identical mobility, each one consisting of two polypeptides with Mr of 47000 and 48000. The same profile was shown by the exoglucanase secreted in the presence of tunicamycin. Antibodies raised
against the protein portion of exoglucanase II did react with both native exoglucanases and their deglycosylated products
with a pattern indicative of immunological identity. Digestion of the “in vitro” deglycosylated products of both exoglucanases
with Staphylococcus aureus V-8 protease or trypsin generated the same proteolytic fragments in each case. Only exoglucanase II was secreted by protoplasts.
These and previously reported results indicate that the protein portions of both isoenzymes may be the product of the same
gene (or a family of related genes), and that exoglucanase I is a product of enzyme II, modified by a process occurring beyond
the permeability barrier of the cell. 相似文献
Genetic structure and diversity of 3789 animals of the Brahman breed from 23 Colombian regions were assessed. Considering the Brahman Zebu cattle as a single population, the multilocus test based on the HW equilibrium, shows significant differences (P < 0.001). Genetic characterization made on the cattle population allowed to examine the genetic variability, calculating a Ho = 0.6621. Brahman population in Colombia was a small subdivision wthin populations (Fit = 0.045), a geographic subdivision almost non-existent or low differentiation (Fst = 0.003) and the Fis calculated (0.042) indicates no detriment to the variability in the population, despite the narrow mating takes place or there is a force that causes the variability is sustained without inbreeding actually affect the cattle population. The outcomes of multivariate analyses, Bayesian inferences and interindividual genetic distances suggested that there is no genetic sub-structure in the population, because of the high rate of animal migration among regions. 相似文献
Plant Molecular Biology - The first biochemical characterization of a chloroplastic disaggregase is reported (Arabidopsis thaliana ClpB3). ClpB3 oligomerizes into active hexamers that resolubilize... 相似文献
The interaction of MinC with FtsZ and its effects on FtsZ polymerization were studied under close to physiological conditions by a combination of biophysical methods. The Min system is a widely conserved mechanism in bacteria that ensures the correct placement of the division machinery at midcell. MinC is the component of this system that effectively interacts with FtsZ and inhibits the formation of the Z-ring. Here we report that MinC produces a concentration-dependent reduction in the size of GTP-induced FtsZ protofilaments (FtsZ-GTP) as demonstrated by analytical ultracentrifugation, dynamic light scattering, fluorescence correlation spectroscopy, and electron microscopy. Our experiments show that, despite being shorter, FtsZ protofilaments maintain their narrow distribution in size in the presence of MinC. The protein had the same effect regardless of its addition prior to or after FtsZ polymerization. Fluorescence anisotropy measurements indicated that MinC bound to FtsZ-GDP with a moderate affinity (apparent KD ∼10 μm at 100 mm KCl and pH 7.5) very close to the MinC concentration corresponding to the midpoint of the inhibition of FtsZ assembly. Only marginal binding of MinC to FtsZ-GTP protofilaments was observed by analytical ultracentrifugation and fluorescence correlation spectroscopy. Remarkably, MinC effects on FtsZ-GTP protofilaments and binding affinity to FtsZ-GDP were strongly dependent on ionic strength, being severely reduced at 500 mm KCl compared with 100 mm KCl. Our results support a mechanism in which MinC interacts with FtsZ-GDP, resulting in smaller protofilaments of defined size and having the same effect on both preassembled and growing FtsZ protofilaments. 相似文献
A modified version of amarantin, main seed storage protein of Amaranthushypochondriacus, carrying four antihypertensive biopeptides Val-Tyr into the acidic-subunit of the protein, was expressed in cell suspension cultures of Nicotiana tabacum L. NT1. Cell growth and viability kinetics were assessed to determine optimal conditions for genetic transformation via Agrobacterium tumefaciens. Selection of putative transgenic calli was conducted using 25 μg ml?1 hygromycin. Presence of the transgene was confirmed using histological glucuronidase assay and PCR analysis. Accumulation and expression of the recombinant protein was detected using Western blot analysis. Protein hydrolysate of transgenic calli showed high levels of inhibition of the angiotensin converting enzyme, with an IC50 value of 3.5 μg ml?1. This was 10-fold lower than that of protein extracts of wild-type cells, with an IC50 of 29.0 μg ml?1. 相似文献
Grape quality for winemaking depends on sugar accumulation and metabolism in berries. Abscisic acid (ABA) and gibberellins (GAs) have been reported to control sugar allocation in economically important crops, although the mechanisms involved are still unknown. The present study tested if ABA and gibberellin A3 (GA3) enhance carbon allocation in fruits of grapevines by modifying phloem loading, phloem area and expression of sugar transporters in leaves and berries. Pot‐grown Vitis vinifera cv. Malbec plants were sprayed with ABA and GA3 solutions. The amount of soluble sugars in leaves and berries related to photosynthesis were examined at three points of berry growth: pre‐veraison, full veraison and post‐veraison. Starch levels and amylase activity in leaves, gene expression of sugar transporters in leaves and berries and phloem anatomy were examined at full veraison. Accumulation of glucose and fructose in berries was hastened in ABA‐treated plants at the stage of full veraison, which was correlated with enhancement of Vitis vinifera HEXOSE TRANSPORTER 2 (VvHT2) and Vitis vinifera HEXOSE TRANSPORTER 6 (VvHT6) gene expression, increases of phloem area and sucrose content in leaves. On the other hand, GA3 increased the quantity of photoassimilates delivered to the stem thus increasing xylem growth. In conclusion, stimulation of sugar transport by ABA and GA3 to berries and stems, respectively, was due to build‐up of non‐structural carbohydrates in leaves, modifications in phloem tissue and modulation in gene expression of sugar transporters. 相似文献
During the induction process of an in vitro callus culture of Argemone mexicana L. (Papaveraceae), the levels of two benzylisoquinoline alkaloids known as berberine and sanguinarine displayed opposing trends. While the berberine levels steadily decreased from the initial explant stage up to the early proliferation of unorganized parenchymatous cell masses, the sanguinarine content increased. Once the callus culture was established, sanguinarine was the primary alkaloid present and berberine could no longer be detected. However, upon shoot regeneration, the berberine accumulation recovered, but sanguinarine was found in the newly formed leafy tissue. After root formation, sanguinarine was relocated to this organ, whereas berberine was evenly distributed between both tissues. Explants from stem internodes did not form callus, and berberine—plus sanguinarine—containing axillary shoots emerged from lateral buds in the induction medium. In contrast to callus-derived shoots, no root formation was observed. Therefore, alkaloid synthesis in A. mexicana in vitro cultures is related to the level of tissue organization in different ways, and while berberine accumulation seems to require the presence of differentiated organs, this is not the case for sanguinarine. Moreover, leafy parts of rootless shoots acquired the capacity to accumulate sanguinarine, which is usually absent in aerial tissues of mature plants. However, when these shoots were rooted, sanguinarine was mainly located in the newly formed roots, while berberine was detected in the shoots at similar levels found in the roots.