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31.
The Nef protein of human immunodeficiency virus type 1 enhances serine phosphorylation of the viral matrix. 总被引:7,自引:5,他引:2 下载免费PDF全文
The human immunodeficiency virus type 1 matrix (MA) protein is phosphorylated during virion maturation on its C-terminal tyrosine and on several serine residues. Whereas MA tyrosine phosphorylation facilitates viral nuclear import, the significance of MA serine phosphorylation remains unclear. Here, we report that MA serine but not tyrosine phosphorylation is strongly enhanced by Nef. Mutations that abrogated the membrane association of Nef and its ability to bind a cellular serine/threonine kinase greatly diminished the extent of virion MA serine phosphorylation. Correspondingly, a protein kinase coimmunoprecipitated with Nef could phosphorylate MA on serine in vitro, producing a phosphopeptide pattern reminiscent of that of virion MA. Recombinant p21-activated kinase hPAK65, a recently proposed relative of the Nef-associated kinase, achieved a comparable result. Taken together, these data suggest that MA is a target of the Nef-associated serine kinase. 相似文献
32.
Isolation of two novel myb-like genes from Arabidopsis and studies on the DNA-binding properties of their products 总被引:2,自引:0,他引:2
Two novel myb-like genes (atmyb6 and atmyb7) were isolated from an Arabidopsis thaliana cDNA library. The entire proteins or the Myb domains encoded by the genes were expressed as fusion proteins in Escherichia coli. The DNA-binding domain of the murine c-Myb was also expressed in the same way for use in comparative studies. The fusion proteins were examined for their DNA-binding activity using the animal c-Myb DNA-binding site (MBS) and the binding site of the maize P gene product (PBS). The Myb domain of Atmyb6 bound to PBS more efficiently than to MBS. Complete Atmyb6 and Atmyb7 proteins preferentially bound to PBS but not MBS. This suggests that the in vitro binding consensus sequences for both Atmyb6 and Atmyb7 are similar to PBS. The binding of the Myb domain of Atmyb6 to both PBS and MBS raises the possibility that the protein recognizes multiple sequences in vivo. The third α-helix and three adjacent amino acids in the third repeat (R3) of c-Myb were replaced with the analogous sequence of Atmyb6 to create a chimeric Myb protein. This chimeric protein bound to PBS with a low affinity but failed to bind to MBS. Thus the binding pattern of the chimeric Myb protein is similar to that of the Atmyb6. This result suggests that the last 20 amino acids in the R3 repeat of Atmyb6 play a major role in DNA-binding. 相似文献
33.
鱼腥藻HB1017株化能异养生长的研究 总被引:5,自引:1,他引:4
以葡萄糖和蔗糖为碳源,检测了六株(种)鱼腥藻的化能异养生产能力。其中鱼腥藻HB1017株化能异养生长较快,鱼腥藻HB0株化能异养生长缓慢,其余四种鱼腥藻不能进行化能异养生长。鱼腥藻HB1017株能利用果糖、葡萄糖、蔗糖为底物进行化能异养生长,但生长速率依次递减,差别显著。8磅湿热灭菌的果糖和蔗糖,与过滤灭菌的相比,只能维持低得多的化能异养生长速率。然而,8磅湿热灭菌的葡萄糖能维持比过滤法灭菌的高得 相似文献
34.
A study was made to observe the effect of cobalt-60 irradiation on the viability of Paragonimus westermani metacercariae in Sinopotamon chekiangense crabs. The crabs were collected in mountain regions of the Zhejiang Province of China in which paragonimiasis is endemic. Adult cats and albino mice were infected with metacercariae irradiated at different doses. Dissection of the host animals was conducted 90 or 30 days, respectively, after infection for recovery of lung flukes. Anti-metacercariae antibody in infected mice was measured by enzyme-linked immunosorbent assay (ELISA). Results showed that metacercariae were unable to grow into adult worms in cats after exposure to gamma irradiation at a dose of 0.10 kGray. However, a small number of metacercariae exposed to a dose of 2.0 kGray excysted and survived in 1 mouse for 30 days. No worm was recovered from mice when the metacercariae were irradiated at a dose of 2.5 kGray. Seropositive results by ELISA were obtained when the mice were infected with metacercariae irradiated at doses ranging from 2.0 to 3.5 kGray. 相似文献
35.
A spin label study of immobilized enzyme spectral subpopulations 总被引:1,自引:0,他引:1
Electron spin resonance (ESR) spin label studies have been carried out to examine the active site conformation of alpha-chymotrypsin before and after immobilization on two types of organic polymer supports: Amberlite XAD-8 and XAD-2. alpha-Chymotryspin was first chemically modified by reaction with methyl-4-phenylbutyrimidate and then inhibited by the active site spin label 4-(2,2,6,6-tetramethyl-piperdine-1-oxyl)-m-flurosulfonylbenzamide. In general, the ESR spectra of the active site lable revealed no significant changes in conformation for most of the enzyme before or after derivatization. On the other hand, two spectral subpopulations (A and B) of spin-labeled enzyme were characterized on the basis of their ESR spectra after immobilization on Amberlite XAD-8. Spectral subpopulation A (distinguished by a highly restrained spectrum) appeared to retain its active site structure and conformation and represented a large majority of the labeled chymotrypsin on the beads. Its presence correlated with the high activity and stability of phenylbutyramidinated chymotryspin on the Amberlite XAD-8 beads. Spectral subpopulation B (distinguished by a very weakly constrained spectrum) appeared to reflect loosely bound or denatured enzyme which was removable upon washing with 40% (v/v) ethylene glycol. Two methods for examining solvent accessibility to the active site lable of the kinetics of ascorbate reduction suggested that both spectral subpopulations had identical accessibilities to the bulk solvent. Paramagnetic broadening of the signal by K(3)Fe(CN)(6) revealed differences in the spin-spin broadening of the A and B components but is deemed and inappropriate indicator of solvent accessibility. 相似文献
36.
Location of helical regions in tetrapyrrole-containing proteins by a helical hydrophobic moment analysis. Application to phytochrome 总被引:1,自引:0,他引:1
Helical regions in many tetrapyrrole proteins are highly amphiphilic, one side interacting with a hydrophobic core and another side interacting with the polar solvent. The mean helical hydrophobic moment is a measure of amphiphilicity of a helix. Helical regions in myoglobin, the alpha and beta subunits of C-phycocyanin, and cytochrome c can be distinguished from nonhelical regions by use of a hydrophobic moment analysis. 24 of 27 (89%) of the helical regions in these proteins were located by this analysis. Calculations were also performed on chymotrypsin, ribonuclease, and papain, which do not possess as pronounced a hydrophobic core as the tetrapyrrole-containing proteins. Less than 50% of the helical regions were correctly located, indicating a lack of amphiphilicity in the helices of these proteins. The hydrophobic moment analysis was also used to predict helical regions in phytochrome, the ubiquitous photoreceptor in plants. Additionally, this analysis is used to quickly locate internal hydrophilic residues which may be functionally important. The distribution of hydrophobic moments from a random sequence was determined so that qualitative and to some extent quantitative comparisons between different amphiphilic helices may be made. 相似文献
37.
Hydrocarbon residues, microbial numbers, and microbial activity were measured and correlated in loam soil contaminated by jet fuel spills resulting in 50 and 135 mg of hydrocarbon g of soil−1. Contaminated soil was incubated at 27°C either as well-aerated surface soil or as poorly aerated subsurface soil. In the former case, the effects of bioremediation treatment on residues, microbial numbers, and microbial activity were also assessed. Hydrocarbon residues were measured by quantitative gas chromatography. Enumerations included direct counts of metabolically active bacteria, measurement of mycelial length, plate counts of aerobic heterotrophs, and most probable numbers of hydrocarbon degraders. Activity was assessed by fluorescein diacetate (FDA) hydrolysis. Jet fuel disappeared much more rapidly from surface soil than it did from subsurface soil. In surface soil, microbial numbers and mycelial length were increased by 2 to 2.5 orders of magnitude as a result of jet fuel contamination alone and by 3 to 4 orders of magnitude as a result of the combination of jet fuel contamination and bioremediation. FDA hydrolysis was stimulated by jet fuel and bioremediation, but was inhibited by jet fuel alone. The latter was traced to an inhibition of the FDA assay by jet fuel biodegradation products. In subsurface soil, oxygen limitation strongly attenuated microbial responses to jet fuel. An increase in the most probable numbers of hydrocarbon degraders was accompanied by a decline in other aerobic heterotrophs, so that total plate counts changed little. The correlations between hydrocarbon residues, microbial numbers, and microbial activity help in elucidating microbial contributions to jet fuel elimination from soil. 相似文献
38.
Pengfei Li Liming Ruan Ruofan Wang Tianqi Liu Gao Song Xiaofei Gao Guohua Jiang Xiaoyan Liu 《仿生工程学报(英文版)》2021,18(6):1378-1390
Nanofibers(NFs)have been widely used in tissue engineering such as wound healing.In this work,the antibacterial ZnO quantum dots(ZnO QDs)have been incorporated into the biocompatible poly(ε-caprolactone)/collagen(PCL/Col)fibrous scaffolds for wound healing.The as-fabricated PCL-Col/ZnO fibrous scaffolds exhibited good swelling,antibacterial activity,and biodegradation behaviors,which were beneficial for the applications as a wound dressing.Moreover,the PCL-Col/ZnO fibrous scaffolds showed excellent cytocompatibility for promoting cell proliferation.The resultant PCL-Col/ZnO fibrous scaffolds containing vascular endothelial growth factor(VEGF)also exhibited promoted wound-healing effect through promoting expression of transforming growth factor-β(TGF-β)and the vascular factor(CD31)in tissues in the early stages of wound healing.This new electrospun fibrous scaffolds with wound-healing promotion and antibacterial property should be convenient for treating wound healing. 相似文献
39.
Shuai Ma Shuhui Sun Jiaming Li Yanling Fan Jing Qu Liang Sun Si Wang Yiyuan Zhang Shanshan Yang Zunpeng Liu Zeming Wu Sheng Zhang Qiaoran Wang Aihua Zheng Shuguang Duo Yang Yu Juan Carlos Izpisua Belmonte Piu Chan Qi Zhou Moshi Song Weiqi Zhang Guang-Hui Liu 《Cell research》2021,(4):415-432
Aging is a major risk factor for many diseases,especially in highly prevalent cardiopulmonary comorbidities and infectious diseases including Coronavirus Diseas... 相似文献
40.