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81.
82.
Self-organization of vegetation in arid ecosystems 总被引:1,自引:0,他引:1
83.
Jolanda?HM?van Bilsen Josée?PA?Wagenaar-Hilbers Maarten?JF?van der Cammen Mariska?EA?van Dijk Willem?van Eden Marca?HM?WaubenEmail author 《Arthritis research & therapy》2002,4(4):R2
We have recently found that matrix metalloproteinases (MMPs) are targets for T-cell and B-cell reactivity in experimental
arthritis. In the present article, we investigate whether modulation of MMP-specific T-cell responses could influence the
course of adjuvant arthritis (AA). Lewis rats were treated nasally with MMP peptides prior to or after AA induction. Administration
of the MMP-10 or the MMP-16 peptide prior to AA induction reduced the arthritic symptoms. In contrast, administration of the
MMP-10 peptide after AA induction aggravated the arthritic symptoms. The present study shows the possible usefulness of MMP
peptides for immunotherapy. However, a clear understanding of proper timing of peptide administration is crucial for the development
of such therapies. 相似文献
84.
Structural variation and functional importance of a D-loop-T-loop interaction in valine-accepting tRNA-like structures of plant viral RNAs 下载免费PDF全文
de Smit MH Gultyaev AP Hilge M Bink HH Barends S Kraal B Pleij CW 《Nucleic acids research》2002,30(19):4232-4240
Valine-accepting tRNA-like structures (TLSs) are found at the 3′ ends of the genomic RNAs of most plant viruses belonging to the genera Tymovirus, Furovirus, Pomovirus and Pecluvirus, and of one Tobamovirus species. Sequence alignment of these TLSs suggests the existence of a tertiary D-loop–T-loop interaction consisting of 2 bp, analogous to those in the elbow region of canonical tRNAs. The conserved G18·Ψ55 pair of regular tRNAs is found to covary in these TLSs between G·U (possibly also modified to G·Ψ) and A·G. We have mutated the relevant bases in turnip yellow mosaic virus (TYMV) and examined the mutants for symptom development on Chinese cabbage plants and for accumulation of genetic reversions. Development of symptoms is shown to rely on the presence of either A·G or G·U in the original mutants or in revertants. This finding supports the existence and functional importance of this tertiary interaction. The fact that only G·U and A·G are accepted at this position appears to result from steric and energetic limitations related to the highly compact nature of the elbow region. We discuss the implications of these findings for the various possible functions of the valine-accepting TLS. 相似文献
85.
Nilsson A Johansson HO Mannesse M Egmond MR Tjerneld F 《Biochimica et biophysica acta》2002,1601(2):138-148
Genetic engineering has been used to construct hydrophobically modified fusion proteins of cutinase from Fusarium solani pisi and tryptophan-containing peptides. The aim was to enhance the partitioning of the tagged protein in a novel aqueous two-phase system formed by only one water-soluble polymer. The system was based on a hydrophobically modified random copolymer of ethylene oxide (EO) and propylene oxide (PO) units, HM-EOPO, with myristyl groups (C(14)H(29)) at both ends. The HM-EOPO polymer is strongly self-associating and has a lower critical solution temperature (cloud point) at 12 degrees C in water. At temperatures above the cloud point a two-phase system is formed with a water top phase and a polymer-enriched bottom phase. By adding a few percent of hydroxypropyl starch polymer, Reppal PES 200, to the system, it is possible to change the densities of the phases so the HM-EOPO-enriched phase becomes the top phase and Reppal-enriched phase is the bottom phase. Tryptophan-based peptides strongly preferred the HM-EOPO rich phase. The partitioning was increased with increasing length of the peptides. Full effect of the tag as calculated from peptide partitioning data was not found in the protein partitioning. When a short spacer was introduced between the protein and the tag the partitioning was increased, indicating a better exposure to the hydrophobic core of the polymer micelle. By adding a hydrophilic spacer between the protein and trp-tag, it was possible to increase the partitioning of cutinase 10 times compared to wild-type cutinase partitioning. By lowering the pH of the system and addition of NaCl, the partitioning of tagged protein was further increased towards the HM-EOPO phase. After isolating the HM-EOPO phase, the temperature was increased and the protein was back-extracted from the HM-EOPO phase to a fresh water phase. 相似文献
86.
Walther TC Pickersgill HS Cordes VC Goldberg MW Allen TD Mattaj IW Fornerod M 《The Journal of cell biology》2002,157(1):63-77
Oxysterol binding proteins (OSBPs) comprise a large conserved family of proteins in eukaryotes. Their ubiquity notwithstanding, the functional activities of these proteins remain unknown. Kes1p, one of seven members of the yeast OSBP family, negatively regulates Golgi complex secretory functions that are dependent on the action of the major yeast phosphatidylinositol/phosphatidylcholine Sec14p. We now demonstrate that Kes1p is a peripheral membrane protein of the yeast Golgi complex, that localization to the Golgi complex is required for Kes1p function in vivo, and that targeting of Kes1p to the Golgi complex requires binding to a phosphoinositide pool generated via the action of the Pik1p, but not the Stt4p, PtdIns 4-kinase. Localization of Kes1p to yeast Golgi region also requires function of a conserved motif found in all members of the OSBP family. Finally, we present evidence to suggest that Kes1p may regulate adenosine diphosphate-ribosylation factor (ARF) function in yeast, and that it may be through altered regulation of ARF that Kes1p interfaces with Sec14p in controlling Golgi region secretory function. 相似文献
87.
Plants are increasingly used as production platforms of various heterologous proteins, but rapid protein turnover can seriously limit the steady-state expression level. Little is known about specific plant proteases involved in this process. In an attempt to obtain potato (Solanum tuberosum cv Desirée) plants resistant to Colorado potato beetle (Leptinotarsa decemlineata Say) larvae, the protease inhibitor equistatin was expressed under the control of strong, light-inducible and constitutive promoters and was targeted to the secretory pathway with and without endoplasmic reticulum retention signal. All constructs yielded similar stepwise protein degradation patterns, which considerably reduced the amount of active inhibitor in planta and resulted in insufficient levels for resistance against Colorado potato beetle larvae. Affinity purification of the degradation products and N-terminal sequencing allowed the identification of the amino acid P(1)-positions (asparagine [Asn]-13, lysine-56, Asn-82, and arginine-151) that were cleaved in planta. The proteases involved in the equistatin degradation were characterized with synthetic substrates and inhibitors. Kininogen domain 3 completely inhibited equistatin degradation in vitro. The results indicate that arginine/lysine-specific and legumain-type Asn-specific cysteine proteases seriously impede the functional accumulation of recombinant equistatin in planta. General strategies to improve the resistance to proteases of heterologous proteins in plants are proposed. 相似文献
88.
Plasma membrane aquaporins are involved in winter embolism recovery in walnut tree 总被引:7,自引:0,他引:7 下载免费PDF全文
Sakr S Alves G Morillon R Maurel K Decourteix M Guilliot A Fleurat-Lessard P Julien JL Chrispeels MJ 《Plant physiology》2003,133(2):630-641
In perennial plants, freeze-thaw cycles during the winter months can induce the formation of air bubbles in xylem vessels, leading to changes in their hydraulic conductivity. Refilling of embolized xylem vessels requires an osmotic force that is created by the accumulation of soluble sugars in the vessels. Low water potential leads to water movement from the parenchyma cells into the xylem vessels. The water flux gives rise to a positive pressure essential for the recovery of xylem hydraulic conductivity. We investigated the possible role of plasma membrane aquaporins in winter embolism recovery in walnut (Juglans regia). First, we established that xylem parenchyma starch is converted to sucrose in the winter months. Then, from a xylem-derived cDNA library, we isolated two PIP2 aquaporin genes (JrPIP2,1 and JrPIP2,2) that encode nearly identical proteins. The water channel activity of the JrPIP2,1 protein was demonstrated by its expression in Xenopus laevis oocytes. The expression of the two PIP2 isoforms was investigated throughout the autumn-winter period. In the winter period, high levels of PIP2 mRNA and corresponding protein occurred simultaneously with the rise in sucrose. Furthermore, immunolocalization studies in the winter period show that PIP2 aquaporins were mainly localized in vessel-associated cells, which play a major role in controlling solute flux between parenchyma cells and xylem vessels. Taken together, our data suggest that PIP2 aquaporins could play a role in water transport between xylem parenchyma cells and embolized vessels. 相似文献
89.
MADS-box protein complexes control carpel and ovule development in Arabidopsis 总被引:28,自引:0,他引:28 下载免费PDF全文
Favaro R Pinyopich A Battaglia R Kooiker M Borghi L Ditta G Yanofsky MF Kater MM Colombo L 《The Plant cell》2003,15(11):2603-2611
The AGAMOUS (AG) gene is necessary for stamen and carpel development and is part of a monophyletic clade of MADS-box genes that also includes SHATTERPROOF1 (SHP1), SHP2, and SEEDSTICK (STK). Here, we show that ectopic expression of either the STK or SHP gene is sufficient to induce the transformation of sepals into carpeloid organs bearing ovules. Moreover, the fact that these organ transformations occur when the STK gene is expressed ectopically in ag mutants shows that STK can promote carpel development in the absence of AG activity. We also show that STK, AG, SHP1, and SHP2 can form multimeric complexes and that these interactions require the SEPALLATA (SEP) MADS-box proteins. We provide genetic evidence for this role of the SEP proteins by showing that a reduction in SEP activity leads to the loss of normal ovule development, similar to what occurs in stk shp1 shp2 triple mutants. Together, these results indicate that the SEP proteins, which are known to form multimeric complexes in the control of flower organ identity, also form complexes to control normal ovule development. 相似文献
90.
Diederik WJ Dippel Eric J van Breda H Bart van der Worp H Maarten A van Gemert Ron J Meijer L Jaap Kappelle Peter J Koudstaal 《BMC cardiovascular disorders》2003,3(1):1-8