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81.
The oxygen-evolving complex (OEC) of higher plant photosystem II (PSII) consists of an inorganic Mn4Ca cluster and three nuclear-encoded proteins, PsbO, PsbP and PsbQ. In this review, we focus on the assembly of these OEC
proteins, and especially on the role of the small intrinsic PSII proteins and recently found “novel” PSII proteins in the
assembly process. The numerous auxiliary functions suggested during the past few years for the OEC proteins will likewise
be discussed. For example, besides being a manganese-stabilizing protein, PsbO has been found to bind calcium and GTP and
possess a carbonic anhydrase activity. In addition, specific roles have been suggested for the two isoforms of the PsbO protein
in Arabidopsis thaliana. PsbP and PsbQ seem to play an additional role in the formation of PSII supercomplexes and in grana stacking, besides their
originally recognized role in providing a proper calcium and chloride ion concentration for water splitting. 相似文献
82.
The yeast Ski complex assists the exosome in the degradation of mRNA. The Ski complex consists of three components; Ski2, Ski3, and Ski8, believed to be present in a 1:1:1 stoichiometry. Measuring the mass of intact isolated endogenously expressed Ski complexes by native mass spectrometry we unambiguously demonstrate that the Ski complex has a hetero-tetrameric stoichiometry consisting of one copy of Ski2 and Ski3 and two copies of Ski8. To validate the stoichiometry of the Ski complex, we performed tandem mass spectrometry. In these experiments one Ski8 subunit was ejected concomitant with the formation of a Ski2/Ski3/Ski8 fragment, confirming the proposed stoichiometry. To probe the topology of the Ski complex we disrupted the complex and mass analyzed the thus formed subcomplexes, detecting Ski8-Ski8, Ski2-Ski3, Ski8-Ski2, and Ski8-Ski8-Ski2. Combining all data we construct an improved structural model of the Ski complex. 相似文献
83.
Charles G. Crispens Philip S. Porter John R. J. Sorenson 《Biological trace element research》1986,10(1):19-24
Plasma copper and zinc levels were measured in SJL/J mice, an inbred strain characterized by a high, spontaneous incidence
of reticulum cell sarcoma (RCS). The changes with age in mean concentrations of these metals were consistent with a physiological
response that is required for remission of neoplasia. Treatment of SJL/J mice with a copper complex, Cu(II)(3,4-diisopropylsalicylate)2 (Cu 3,5-DIPS), dissolved in a 10% Tween 80-saline solution revealed a decrease in survival and decline in the incidence of
RCS at 52 wk of age. The toxic effects of Cu 3,5-DIPS therapy appeared to be related to the intraperitoneal route of administration
and to extracellular deposition of collagen. The inhibitory effect on tumor development was not related to Cu 3,5-DIPS. Rather,
Tween 80 was found to be the factor of importance. 相似文献
84.
In Drosophila, the 255kDa catalytic subunit (dpolεp255) and the 58kDa subunit of DNA polymerase ε (dpolεp58) have been identified. The N-terminus of dpolεp255 carries well-conserved six DNA polymerase subdomains and five 3'→5' exonuclease motifs as observed with Polε in other species. We here examined roles of dpolεp255 during Drosophila development using transgenic fly lines expressing double stranded RNA (dsRNA). Expression of dpolεp255 dsRNA in eye discs induced a small eye phenotype and inhibited DNA synthesis, indicating a role in the G1-S transition and/or S-phase progression of the mitotic cycle. Similarly, expression of dpolεp255 dsRNA in the salivary glands resulted in small size and endoreplication defects, demonstrating a critical role in endocycle progression. In the eye disc, defects induced by knockdown of dpolεp255 were rescued by overexpression of the C-terminal region of dpolεp255, indicating that the function of this non-catalytic domain is conserved between yeast and Drosophila. However, this was not the case for the salivary gland, suggesting that the catalytic N-terminal region is crucial for endoreplication and its defect cannot be complemented by other DNA polymerases. In addition, several genetic interactants with dpolεp255 including genes related to DNA replication such as RFC, DNA primase, DNA polη, Mcm10 and Psf2 and chromatin remodeling such as Iswi were also identified. 相似文献
85.
The protozoan parasite Leishmania donovani encounters large fluctuations in osmolality as it cycles between its insect vector and human host. The flagellated promastigote exhibits regulatory volume responses involving organic and inorganic osmolytes, but little is known about volume regulation in the clinically relevant amastigote that multiplies within the parasitophorous vacuoles of mammalian host cells. Using a combination of morphological, X-ray microanalytical, and biochemical approaches we determined that non-motile amastigotes respond to hypotonic stress with (1) an amino acid and l-alanine-mediated regulatory volume decrease, and (2) a parallel release of Na+, K+, P (presumably as negatively charged phosphates), and subsequently Cl- from cytoplasm and the cell as a whole. In addition P, Zn2+, and subsequently Ca2+ increase in acidocalcisomes as Cl- content declines in this compartment. This evidence is the first to document subcellular translocation of, and thus a potential role for, zinc in volume regulatory responses. These coordinated changes in organic and inorganic osmolytes demonstrate that amastigote subcellular compartments, particularly acidocalcisomes, function in maintaining ionic homeostasis in the response of Leishmania amastigotes to hypo-osmotic stress. 相似文献
86.
近年来全球慢性乙型肝炎(chronic hepatitis B,CHB)防治指南提出了“功能性治愈”(functional cure)的概念,即患者经过治疗达到血清乙型肝炎病毒表面抗原(hepatitis B virus surface antigen,HBsAg)消失,但现有抗病毒治疗很难实现这一目标。本研究对既往临床试验中经抗原抗体复合物型治疗性疫苗(乙克)治疗后的CHB患者HBsAg下降情况进行了归纳分析,结果显示,经乙克治疗随访后达到乙型肝炎e抗原(hepatitis B e antigen,HBeAg)血清学转换者的HBsAg下降高达0.95log10IU/mL,显著高于未达到HBeAg血清学转换者的0.32log10IU/mL(P<0.01),而经氢氧化铝佐剂治疗随访后发生HBeAg血清学转换(0.49log10IU/mL)者与未发生HBeAg血清学转换者(0.36log10IU/mL)之间HBsAg下降无统计学差异。乙克组治疗过程中,丙氨酸氨基转移酶(alanine aminotransferase,ALT)骤升(ALT flare)在HBsAg下降>1.0log10IU/mL者中较多见,氢氧化铝组未观察到此现象。回归分析显示,乙克治疗后HBsAg下降的影响因素有患者出现HBeAg血清学转换、感染的HBV为B基因型、治疗过程中ALT出现10倍增高,以及基线血清HBsAg为高水平。结果提示,乙克诱导的特异性免疫对降低CHB患者血清HBsAg水平有一定效果,采用“抗病毒药物治疗+针对HBsAg的中和性抗体被动免疫+乙克主动免疫”的“三明治”治疗策略可能会提高“功能性治愈”率。 相似文献
87.
Thompson JA Srivastava MK Bosch JJ Clements VK Ksander BR Ostrand-Rosenberg S 《Cancer immunology, immunotherapy : CII》2008,57(3):389-398
Activation of tumor-reactive T lymphocytes is a promising approach for the prevention and treatment of patients with metastatic
cancers. Strategies that activate CD8+ T cells are particularly promising because of the cytotoxicity and specificity of CD8+ T cells for tumor cells. Optimal CD8+ T cell activity requires the co-activation of CD4+ T cells, which are critical for immune memory and protection against latent metastatic disease. Therefore, we are developing
“MHC II” vaccines that activate tumor-reactive CD4+ T cells. MHC II vaccines are MHC class I+ tumor cells that are transduced with costimulatory molecules and MHC II alleles syngeneic to the prospective recipient. Because
the vaccine cells do not express the MHC II-associated invariant chain (Ii), we hypothesized that they will present endogenously synthesized tumor peptides that are not presented by professional Ii+ antigen presenting cells (APC) and will therefore overcome tolerance to activate CD4+ T cells. We now report that MHC II vaccines prepared from human MCF10 mammary carcinoma cells are more efficient than Ii+ APC for priming and boosting Type 1 CD4+ T cells. MHC II vaccines consistently induce greater expansion of CD4+ T cells which secrete more IFNγ and they activate an overlapping, but distinct repertoire of CD4+ T cells as measured by T cell receptor Vβ usage, compared to Ii+ APC. Therefore, the absence of Ii facilitates a robust CD4+ T cell response that includes the presentation of peptides that are presented by traditional APC, as well as peptides that
are uniquely presented by the Ii− vaccine cells. 相似文献
88.
Cintia D. Medina Luciano J. Avila Jack W. Sites Jr Mariana Morando 《Biological journal of the Linnean Society. Linnean Society of London》2014,113(1):256-269
This study presents a detailed phylogeographical analysis of one of the most conspicuous groups of lizards in northwestern Patagonia, the Liolaemus kriegi complex. This region is geographically very complex as a result of Andean orogeny and subsequent volcanism coupled with a long history of glaciations and climatic changes. For 247 individuals we sequenced one mitochondrial gene (cytochrome b) and for a subset we sequenced another mitochondrial gene [12S ribosomal RNA (12S)] and two nuclear fragments [kinesin family member 24 (KIF24) and BA3 ribosomal RNA (BA3)]. We obtained gene trees and mitochondrial and nuclear haploytpe networks, and estimated genetic distances between the main lineages and basic molecular diversity indices. We also performed spatial analysis of molecular variance (SAMOVA) and Bayesian Skyline Plot (BSP) analyses, and concordant patterns from different lines of evidence permitted delimitation of seven lineages: two described species, Liolaemus buergeri and Liolaemus tregenzai; four candidate species, Liolaemus sp. A, Liolaemus sp. B, Liolaemus sp. C, and Liolaemus sp. D; and one lineage that includes all individuals from the geographical range of Liolaemus ceii and L. kriegi, referred to as L. kriegi + L. ceii. We discuss the evolutionary processes that may contribute to the origin of these lineages and their taxonomic and conservation implications. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 256–269. 相似文献
89.
90.
Adonis McQueen Lynn D. Blake Ala Azhari M. Trent Kemp Tommy W. McGaha Niranjan Namelikonda Randy W. Larsen Roman Manetsch Dennis E. Kyle 《Bioorganic & medicinal chemistry letters》2017,27(20):4597-4600
Primaquine (PQ) is the only commercially available drug that clears dormant liver stages of malaria and blocks transmission to mosquito vectors. Although an old drug, much remains to be known about the mechanism(s) of action. Herein we develop a fluorescent tagged PQ to discover cellular localization in the human malaria parasite, Plasmodium falciparum. Successful synthesis and characterization of a primaquine-coumarin fluorescent probe (PQCP) demonstrated potency equivalent to the parent drug and the probe was not cytotoxic to HepG2 carcinoma cells. Cellular localization was found primarily in the cytosol of the asexual erythrocytic and gametocyte stages of parasite development. 相似文献