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Stanislav Isayenkov Jean-Charles Isner Frans JM Maathuis 《Plant signaling & behavior》2011,6(8):1201-1204
Potassium (K) is one of the major nutrients that is essential for plant growth and development. The majority of cellular K+ resides in the vacuole and tonoplast K+ channels of the TPK (Two Pore K) family are main players in cellular K+ homeostasis. All TPK channels were previously reported to be expressed in the tonoplast of the large central lytic vacuole (LV) except for one isoform in Arabidopsis that resides in the plasma membrane. However, plant cells often contain more than one type of vacuole that coexist in the same cell. We recently showed that two TPK isoforms (OsTPKa and OsTPKb) from Oryza sativa localize to different vacuoles with OsTPKa predominantly found in the LV tonoplast and OsTPKb primarily in smaller compartments that resemble small vacuoles (SVs). Our study further revealed that it is the C-terminal domain that determines differential targeting of OsTPKa and OsTPKb. Three C-terminal amino acids were particularly relevant for targeting TPKs to their respective endomembranes. In this addendum we further evaluate how the different localization of TPKa and TPKb impact on their physiological role and how TPKs provide a potential tool to study the physiology of different types of vacuole.Key words: TPK channels, small vacuoles, vacuolar targeting, potassiumThe roles of plant vacuolar K+ channels are diverse and include potassium homeostasis, turgor regulation and responses to abiotic stress. Vacuolar K+-selective channels belong to two-pore K+ (TPK) channel families which have been found in genomes of many plant species such as Arabidopsis, poplar, Physcomitrella, Eucalyptus, barley, potato, rice and tobacco (Fig. 1). TPKs have structural similarity to mammalian “tandem P domain” channels with a secondary structure that contains four transmembrane domains and two pore regions (Fig. 2).1–5 TPK channels have pore regions with a GYGD signature that endows K+ selectivity and a variable number of Ca2+ binding EF domains in the C terminus.3–8 One of the best characterized members of the TPK family is AtTPK1 from Arabidopsis thaliana. AtTPK1 activity is voltage independent but sensitive to cytosolic Ca2+, cytosolic pH and N-terminal phosphorylation by 14-3-3 proteins.5,6,8,9 In Arabidopsis, AtTPK1 expresses in the large lytic vacuole (LV) and plays roles in cellular K+ homeostasis, K+-release during stomatal closure and seed germination.4,5 Other members of the Arabidopsis TPK family (AtTPK2, AtTPK3, AtTPK5) have been shown to localize to the LV but also showed some expression in smaller, vesicle-like, compartments.4 However, none of these isoforms appears to form functional channels in planta although our experiments with heterologous expression of AtTPK3 and AtTPK5 in the K+ uptake deficient E. coli LB2003 demonstrates complementation of bacterial growth phenotype (Isayenkov S, et al. unpublished results). Equally intriguing, is the plasma membrane localization of the Arabidopsis TPK4 isoform, in spite of its sequence being very similar to that of other TPKs.10Open in a separate windowFigure 1Phylogenetic tree of plant TPKs. The three main clusters of TPKs comprise: Cluster 1 with AtTPK1-like channels; Cluster 2 with AtTPK3/TPK5-like channels; Cluster 3 with barley HvTPKb. Bootstrap analysis was performed using ‘Molecular Evolutionary Genetics Analysis, MEGA4’ software available at www.megasoftware.net/mega4/megaOpen in a separate windowFigure 2Two-pore potassium channel secondary structure. TPK channels comprise four transmembrane domains (1–4) and two pore regions (P) per subunit. Functional channels are formed from two subunits. In most TPKs, both P regions contain a K+ selectivity signature, GYGD. However, the tobacco NtTPKa isoform has different motifs in the second P domain. In the N terminal region, TPKs have a 14-3-3 binding domain that impact on channel activity, with the binding of 14-3-3 protein leading to channel activation. C-termini of TPKs show a varying number of putative Ca2+ binding “EF hands” which may vary from zero to two. 相似文献
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85.
Hans-Alfred Kirchner 《Cell and tissue research》1934,22(1):1-19
Ohne Zusammenfassung 相似文献
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Brachmann AO Kirchner F Kegler C Kinski SC Schmitt I Bode HB 《Journal of biotechnology》2012,157(1):96-99
The production of the blue pigment indigoidine has been achieved in the entomopathogenic bacterium Photorhabdus luminescens by a promoter exchange and in Escherichia coli following heterologous expression of the biosynthesis gene indC. Moreover, genes involved in the regulation of this previously “silent” biosynthesis gene cluster have been identified in P. luminescens. 相似文献
88.
Kirchner S Seixas P Kaushik S Panserat S 《Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology》2005,140(2):333-340
The objective of the study described here was to analyze in rainbow trout (Oncorhynchus mykiss) the effects of low protein intake on peripheral glucose phosphorylation capacities and gluconeogenic enzymes in kidney and intestine. Fish were food-deprived for 14 days or kept under a low and a high protein intake regime using a pair feeding protocol in order to maintain constant carbohydrate and lipid intakes. We analyzed the effect of protein restriction on (i) hepatic, renal and intestinal fructose-1.6-bisphophatase (FBPase) and glucose-6-phosphatase (G6Pase) enzymes at the molecular and enzymatic levels and (ii) glucose phosphorylation activities (hexokinases) in the liver, peri-visceral adipose tissue, red muscle and white muscle. Irrespective of the nutritional status, we observed the same levels of hexokinase activities in all the tissues studied. Renal G6Pase and FBPase gene expression and activities were not modified among the groups. In contrast, there was increased intestinal FBPase gene expression in fish under a low protein intake and higher G6Pase activities in both groups of fed fish. This result differs from what is observed in rats and suggest a role of intestine in the regulation of postprandial gluconeogenesis in fed trout. In conclusion, our data did not demonstrate any specific effect of low dietary protein intake to either gluconeogenic capacities or glucose phosphorylation capacities in rainbow trout. 相似文献
89.
Haringman JJ Vinkenoog M Gerlag DM Smeets TJ Zwinderman AH Tak PP 《Arthritis research & therapy》2005,7(4):R862-R867
Analysis of biomarkers in synovial tissue is increasingly used in the evaluation of new targeted therapies for patients with
rheumatoid arthritis (RA). This study determined the intrarater and inter-rater reliability of digital image analysis (DIA)
of synovial biopsies from RA patients participating in clinical trials. Arthroscopic synovial biopsies were obtained before
and after treatment from 19 RA patients participating in a randomized controlled trial with prednisolone. Immunohistochemistry
was used to detect CD3+ T cells, CD38+ plasma cells and CD68+ macrophages. The mean change in positive cells per square millimetre for each marker was determined by different operators
and at different times using DIA. Nonparametric tests were used to determine differences between observers and assessments,
and to determine changes after treatment. The intraclass correlations (ICCs) were calculated to determine the intrarater and
inter-rater reliability. Intrarater ICCs showed good reliability for measuring changes in T lymphocytes (R = 0.87), plasma
cells (R = 0.62) and macrophages (R = 0.73). Analysis by Bland–Altman plots showed no systemic differences between measurements.
The smallest detectable changes were calculated and their discriminatory power revealed good response in the prednisolone
group compared with the placebo group. Similarly, inter-rater ICCs also revealed good reliability for measuring T lymphocytes
(R = 0.68), plasma cells (R = 0.69) and macrophages (R = 0.72). All measurements identified the same cell types as changing
significantly in the treated patients compared with the placebo group. The measurement of change in total positive cell numbers
in synovial tissue can be determined reproducibly for various cell types by DIA in RA clinical trials. 相似文献
90.
David Benito-Garagorri Christina M. Standfest-Hauser Karl Kirchner 《Inorganica chimica acta》2010,363(14):3674-1759
The synthesis of bidentate aminophosphine ligands (PNquin) based on 8-hydroxyquinoline is described. These ligands react with cis-Fe(CO)4Br2 to give selectively octahedral complexes of the type cis,cis-Fe(PNquin)(CO)2Br2. There is only one isomer formed where the two CO and the two bromide ligands adopt a cis configuration. The reaction of [RuCp(CH3CN)3]PF6 with PNquin ligands affords the halfsandwich complexes [RuCp(PNquin)(CH3CN)]PF6 in high isolated yields. Likewise, treatment of [Ru(η6-p-cymene)(μ-Cl)Cl]2 with PNquin in the presence of AgCF3SO3 affords halfsandwich complexes of the type [Ru(η6-p-cymene)(PNquin)Cl]CF3SO3. All ligands and complexes are characterized by NMR and IR spectroscopy. The X-ray structure of representative compounds is reported. In addition, the relative stability of isomeric structures and conformers of Fe(PNquin-Ph)(CO)2Br2 is studied by means of DFT calculations. 相似文献