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901.
Markus Albert Anna K. Jehle Martin Lipschis Katharina Mueller Yi Zeng Georg Felix 《European journal of cell biology》2010,89(2-3):200-207
In this review we focus on pattern recognition receptors in plants that detect extracellular signals indicative for pathogen attack and injury. We start out with a discussion on FLS2, which binds and responds to bacterial flagellin, and then concentrate on ligand–receptor interactions as initial steps in the molecular receptor activation process. Comparison with other receptor kinases, whether involved in plant immunity or regulation of other cellular programs, might indicate common principles of receptor activation. 相似文献
902.
Regulation of alternative oxidase activity during phosphate deficiency in bean roots (Phaseolus vulgaris) 总被引:2,自引:0,他引:2
Cyanide-resistant respiration was studied in mitochondria isolated from the roots of bean plants ( Phaseolus vulgaris L. cv. Złota Saxa) grown hydroponically up to 16 days on a phosphate-sufficient (+P, control) or phosphate-deficient (−P) medium. Western blotting indicated that the alternative oxidase (AOX) was present only in its reduced (active) form, both in phosphate-sufficient and phosphate-deficient roots, but in the latter, the amount of AOX protein was greater. Addition of pyruvate to the isolation, washing and reaction media made mitochondria from +P roots cyanide-insensitive, similar to mitochondria from −P roots. The doubled activity of NAD-malic enzyme (NAD-ME) in −P compared with +P root mitochondria may suggest increased pyruvate production in −P mitochondria. Lower cytochrome c oxidase (COX) activity and no uncoupler effect on respiration indicated limited cytochrome chain activity in −P mitochondria. In −P mitochondria, the oxygen uptake decreased and the level of Q reduction increased from 60 to 80%. With no pyruvate present (AOX not fully activated), inhibition of the cytochrome pathway resulted in an increased level of the ratio of reduced ubiquinone (Qr) to total ubiquinone (Qt) (Qr/Qt) in +P mitochondria, but did not change Qr/Qt in −P mitochondria. When pyruvate was present, the kinetics for AOX were similar in mitochondria from −P and +P roots. It is suggested that AOX participation in −P respiration may provide an acclimation to phosphate deficiency. Stabilization of the ubiquinone reduction level by AOX might prevent the harmful effect of an increased formation of reactive oxygen species. 相似文献
903.
Removal of the embryonic axis prevents the normal decline of carboxypeptidase (Cpase) I in mung bean seedling cotyledons. Cpase I activity and protein, the latter manifested on western blots, almost completely disappear about 24 h before the cotyledon abscises. Of the 3 proteolytic enzyme patterns, only that of Cpase I can be restored by an exogenous supply of 10 m M CaCl2 in the agar growth medium. The calcium effect is dependent on [CaCl2 ] and is not manifested in the presence of chelators and calcium channel blockers. For detached cotyledons to show the normal low level of Cpase I by the eighth day of growth, calcium had to be supplied during seed imbibition and throughout the entire time from removal of the axis. The difference between detached cotyledons in the absence and presence of calcium was greatest when the cotyledons were detached 4–6 days after seed imbibition. Loss of Cpase I activity and protein can be demonstrated in vitro, with the maximum level of Cpase I-degrading activity measured 4 days after seed imbibition under the same growth conditions used to study the calcium effect. It is sensitive to pepstatin and has a pH optimum of 3, suggesting that this Cpase I-degrading activity is due to an aspartic protease. 相似文献
904.
-N-Acetyl-d-hexosaminidase from Aspergillus oryzae catalysed the stereo- and regiospecific formation of the 6-O-benzylated disaccharide derivatives GalNAc1-3(6- OBn)Gal-SEt and GlcNAc1-3(6-OBn)Gal-SEt, which were obtained in transglycosylation reactions employing ethyl 6- O-benzyl-1-thio--d-galactopyranoside as acceptor. Preparative amounts of the chitobiose derivative GlcNAc1- 3GlcNAc-OPhNO2-p was prepared as well. - N-Acetyl-d-hexosaminidase from bovine testes catalysed the specific synthesis of GlcNAc1-3(6-OBn)GlcNH2-SEt and GalNAc1-3(6-OBn)GlcNH2-SEt, employing ethyl 2-amino-6-O-benzyl-2-deoxy-1-thio--d-glucopyranoside as acceptor. -d-Glucuronidase from E. coli was found to catalyse the formation of GlcA1-3(6-OBn)GlcNH2- SEt employing the same acceptor. 相似文献
905.
Sandro Sonnino Paola Brocca Domenico Acquotti Anna Bernardi Laura Raimondi Makoto Kiso Hideharu Ishida Su-Chen Li Yu-Teh Li 《Bioscience reports》1999,19(3):163-168
The conformational properties of GM2, GalNac-4(Neu5Ac-3) Gal-4Glc-1Cer have been compared to those of 6-GM2, in which the linkage between the GalNAc and Gal was altered from GalNac-4Gal- to GalNac-6Gal-, and to those of GD1a, Neu5Ac-3Gal-3GalNAc-4(Neu5Ac-3)Gal-4Glc-1Cer, and GalNAc-GD1a.Our results revealed that unlike the compact and rigid oligosaccharide head group found in GM2, where the Neu5Ac and the GalNAc residues interact, the sugar chain of 6-GM2 is in an open spatial arrangement, with the Neu5Ac no longer interacting with GalNAc, freely accessible to external interactions.The structure of GD1a can be regarded as that of GM2 with an extension of the terminal Neu5Ac-3Gal-disaccharide. The inner portion of GD1a is that of GM2 comprising the very rigid GalNAc-[Neu5Ac-]Gal trisaccharide. The terminal Neu5Ac-Gal linkage is flexible and fluctuates between two limiting conformations. In GalNAc-GD1a the outer sialic acid gains conformational rigidity due to the presence of the outer GalNAc in position 4 of galactose. This ganglioside has two core GalNAc-[Neu5Ac-]Gal trisaccharide linked in tandem. 相似文献
906.
Natuzzi D Daddabbo L Stipani V Cappello AR Miniero DV Capobianco L Stipani I 《Journal of bioenergetics and biomembranes》1999,31(6):535-541
The effect of pyridoxal 5-phosphate and some other lysine reagents on the purified,reconstituted mitochondrial oxoglutarate transport protein has been investigated. The inhibition ofoxoglutarate/oxoglutarate exchange by pyridoxal 5-phosphate can be reversed by passing theproteoliposomes through a Sephadex column but the reduction of the Schiff's base by sodiumborohydride yielded an irreversible inactivation of the oxoglutarate carrier protein. Pyridoxal5-phosphate, which caused a time- and concentration-dependent inactivation of oxoglutaratetransport with an IC50 of 0.5 mM, competed with the substrate for binding to the oxoglutaratecarrier (K
i
= 0.4 mM). Kinetic analysis of oxoglutarate transport inhibition by pyridoxal5-phosphate indicated that modification of a single amino acid residue/carrier molecule wassufficient for complete inhibition of oxoglutarate transport. After reduction with sodiumborohydride [3H]pyridoxal 5-phosphate bound covalently to the oxoglutarate carrier. Incubation ofthe proteoliposomes with oxoglutarate or L-malate protected the carrier against inactivationand no radioactivity was found associated with the carrier protein. In contrast, glutarate andsubstrates of other mitochondrial carrier proteins were unable to protect the carrier. Mersalyl,which is a known sulfhydryl reagent, also failed to protect the oxoglutarate carrier againstinhibition by pyridoxal 5-phosphate. These results indicate that pyridoxal 5-phosphateinteracts with the oxoglutarate carrier at a site(s) (i.e., a lysine residue(s) and/or the amino-terminalglycine residue) which is essential for substrate translocation and may be localized at or nearthe substrate-binding site. 相似文献
907.
Saposins and Their Interaction with Lipids 总被引:2,自引:0,他引:2
Vaccaro Anna Maria Salvioli Rosa Tatti Massimo Ciaffoni Fiorella 《Neurochemical research》1999,24(2):307-314
The lysosomal degradation of several sphingolipids requires the presence of four small glycoproteins called saposins, generated by proteolytic processing of a common precursor, prosaposin. Saposins share several structural properties, including six similarly located cysteines forming three disulfide bridges with the same cysteine pairings. Recently it has been noted that also other proteins have the same polypeptide motif characterized by the similar location of six cysteines. These saposin-like (SAPLIP) proteins are surfactant protein B (SP-B), Entamoeba histolytica poreforming peptide, NK-lysin, acid sphingomyelinase and acyloxyacyl hydrolase. The structural homology and the conserved disulfide bridges suggest for all SAPLIPs a common fold, called saposin fold. Up to now a precise fold, comprising five -helices, has been established only for NK-lysin. Despite their similar structure each saposin promotes the degradation of specific sphingolipids in lysosomes, e.g. Sap B that of sulfatides and Sap C that of glucosylceramides. The different activities of the saposins must reside within the module of the -helices and/or in additional specific regions of the molecule. It has been reported that saposins bind to lysosomal hydrolases and to several sphingolipids. Their structural and functional properties have been extensively reviewed and hypotheses regarding their molecular mechanisms of action have been proposed. Recent work of our group has evidenced a novel property of saposins: some of them undergo an acid-induced change in hydrophobicity that triggers their binding to phospholipid membranes. In this article we shortly review recent findings on the structure of saposins and on their interactions with lipids, with special attention to interactions with phospholipids. These findings offer a new approach for understanding the physiological role of saposins in lysosomes. 相似文献
908.
909.
Gene-targeted mice lacking the Trex1 (DNase III) 3'-->5' DNA exonuclease develop inflammatory myocarditis
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Morita M Stamp G Robins P Dulic A Rosewell I Hrivnak G Daly G Lindahl T Barnes DE 《Molecular and cellular biology》2004,24(15):6719-6727
TREX1, originally designated DNase III, was isolated as a major nuclear DNA-specific 3'-->5' exonuclease that is widely distributed in both proliferating and nonproliferating mammalian tissues. The cognate cDNA shows homology to the editing subunit of the Escherichia coli replicative DNA polymerase III holoenzyme and encodes an exonuclease which was able to serve a DNA-editing function in vitro, promoting rejoining of a 3' mismatched residue in a reconstituted DNA base excision repair system. Here we report the generation of gene-targeted Trex1(-/-) mice. The null mice are viable and do not show the increase in spontaneous mutation frequency or cancer incidence that would be predicted if Trex1 served an obligatory role of editing mismatched 3' termini generated during DNA repair or DNA replication in vivo. Unexpectedly, Trex1(-/-) mice exhibit a dramatically reduced survival and develop inflammatory myocarditis leading to progressive, often dilated, cardiomyopathy and circulatory failure. 相似文献
910.
Mechanical forces related to pressure and flow are important for cell hypertrophy and proliferation. There are still a few studies that examine responses of human vascular smooth muscle cells to pure pressure stress (transmural pressure). It is unclear as to which mechanisms are involved in cellular responses to pressure elevation. On the other hand, although the involvement of the local renin-angiotensin system (RAS) in pressure-induced responses was reported, the results were contradictory. It still remains to be determined whether RAS in human vascular smooth muscle cells is activated by pure pressure stress. We studied the upstream signal transduction events of extracellular signal kinase (ERK) in response to atmospheric pressure stress and involvement of angiotensin II in pressure-induced cell proliferation in human aortic smooth muscle cells (HASMC). A pressure-loading apparatus was set up to examine the effects of atmospheric pressure on human aortic smooth muscle cells. Pressure application of 160 mmHg for 3 h produced cell proliferation and activated ERK and c-JUN N-terminal kinase (JNK). ACE inhibitor suppressed all of them. ERK kinase (MEK) inhibitor also suppressed cell proliferation stimulated by pure pressure. The phosphorylated c-Src was increased by pure pressure stress. The treatment with c-Src kinase inhibitor suppressed pressure-induced proliferative response. In summary, our study found that ERK activation mediated pure pressure-induced proliferative response of HASMC. This activation was partly mediated by c-Src. 相似文献