Phospholipid hydroperoxide glutathione peroxidase is an antioxidant enzyme that has the highest capability of reducing membrane-bound hydroperoxy lipids as compared to free organic and inorganic hydroperoxides amongst the glutathione peroxidases.In this study,urea-induced effects on the inactivation and unfolding of a recombinant phospholipid hydroperoxide glutathione peroxidase(PHGPx)from Oryza sativa were investigated by means of circular dichroism and fluorescence spectroscopy.With the increase of urea concentration,the residual activity of OsPHGPx decreases correspondingly.When the urea concentration is above 5.0 mol/L,there was no residual activity.In addition,the observed changes in intrinsic tryptophan fluorescence,the binding of the hydrophobic fluorescence probe ANS,and the far UV CD describe a common dependence on the concentration of urea suggesting that the conformational features of the native OsPHGPx are lost in a highly cooperative single transition.The unfolding process comprises of three zones:the native base-line zone between 0 and 2.5 mol/L urea,the transition zone between 2.5 and 5.5 mol/L urea,and the denatured base-line zone above 5.5 mol/L urea.The transition zone has a midpoint at about 4.0 mol/L urea.
WANG FengZHOU Hui-pingKONG Bao-huaFAN Jing-huaCHEN Hai-ruLIU Jin-yuan
萝卜磷脂氢谷胱甘肽过氧化物酶(RsPHGPx)是一个定位于线粒体的蛋白质.为了阐明该蛋白质线粒体定位信号的准确切割位点,采用了免疫亲和层析方法纯化天然的RsPHGPx.用重组RsPHGPx 蛋白免疫兔子获得了抗RsPHGPx 的多克隆抗血清,以重组RsPH G Px 蛋白为配体,采用亲和层析技术对抗血清进行了纯化,得到了单特异性的抗RsPHGPx 的抗体.将纯化好的抗体偶联到一个N-羟基琥珀酰亚胺(NHS)预先激活的琼脂糖柱子上,装配成一个以单特异性的抗RsPHGPx 抗体为配体的免疫亲和层析柱.经过对纯化条件的摸索和优化,形成了一个简单、特异的一步法纯化方案.按照该方案,从萝卜幼苗线粒体总蛋白质提取物中纯化到一个分子质量与预期值相一致的特异蛋白质.免疫印迹分析表明,该蛋白质被抗RsPH G Px 的抗血清特异识别.酶活性分析表明,该蛋白质具有显著的PH G Px 活性.这些结果表明,纯化到的特异蛋白质是萝卜的RsPH G Px天然蛋白.这是首个关于定位于植物细胞器的PH G Px 蛋白纯化的报道.这一结果为准确测定RsPH G Px 信号肽的切割位点奠定了基础,并将有助于对植物PH G Px 的亚细胞定位机制及其生理功能的深入研究.
The transcription factors DREB1s/CBFs play important roles in the regulation of plant resistance to environmental stresses and are quite useful for generating transgenic plants tolerant to these stresses. In the present work, a cDNA encoding DREB1/CBF-like protein (GhDREB1L) from cotton was isolated, and its sequence features, DNA binding preference, and expression patterns of the transcripts were also characterized. GhDREB1L contained one conserved AP2/ERF domain and its amino acid sequence was similar to the DREB1/CBF group of the DREB family from other plants. The DNA-binding domain of GhDREB1L was successfully expressed as a fusion protein in Escherichia coli BL21 (DE3) and purified by Ni-NTA affinity chromatography. Electrophoretic mobility shift assay revealed that the purified GhDREB1L fusion protein had a specific binding activity with the previously characterized DRE ele-ment (core sequence, ACCGAC) and also with the DRE-like sequence (core sequence, GCCGAC) in the promoter of the dehydration-responsive late embryogenesis-abundant gene LEA D113. Semi-quantita- tive RT-PCR showed that GhDREB1L was induced in the cotton cotyledons by low temperature, as well as drought and NaCl treatments. These results suggested that the novel cotton GhDREB1L might play an important role in response to low temperature as well as drought and high salinity through binding to the DRE cis-element.
HUANG Bo, JIN LongGuo & LIU JinYuan Laboratory of Molecular Biology and Protein Science Laboratory of the Ministry of Education, Department of Biological Sciences and Biotechnology, Tsinghua University, Beijing 100084, China
