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81.
Malgorzata Kloc Matthew T Dougherty Szczepan Bilinski Agnes P Chan Eric Brey Mary Lou King Charles W Patrick Laurence D Etkin 《Developmental biology》2002,241(1):79-93
The germ plasm is a specialized region of oocyte cytoplasm that contains determinants of germ cell fate. In Xenopus oocytes, the germ plasm is a part of the METRO region of mitochondrial cloud. It contains the germinal granules and a variety of coding and noncoding RNAs that include Xcat2, Xlsirts, Xdazl, DEADSouth, Xpat, Xwnt11, fatVg, B7/Fingers, C10/XFACS, and mitochondrial large and small rRNA. We analyzed the distribution of these 11 different RNAs within the various compartments of germ plasm during Xenopus oogenesis and development by using whole-mount electron microscopy in situ hybridization. Serial EM sections were used to reconstruct a three-dimensional image of germinal granule distribution within the METRO region of the cloud and the distribution of RNAs on the granules in oocytes and embryos. We found that, in the oocytes, the majority of RNAs were associated either with the precursor of germinal granules or with the germ plasm matrix. Only Xcat2, Xpat, and DEADSouth RNAs were associated with the mature germinal granules in oocytes, while only Xcat2 and Xpat were associated with germinal granules in embryos. However, Xcat2 was the only RNA that was consistently sequestered inside the germinal granules, while the others were located on the periphery. Xdazl, which functions in germ cell migration/formation, was detected on the matrix between granules. Later in development, Xcat2 mRNA was released from the germinal granules. This coincides with the timing of its translational derepression. These results demonstrate that there is a dynamic three-dimensional architecture to the germinal granules that changes during oogenesis and development. They also indicate that association of specific RNAs with the germinal granules is not a prerequisite for their serving a germ cell function; however, it may be related to their state of translational repression. 相似文献
82.
83.
Pászty K Penheiter AR Verma AK Padányi R Filoteo AG Penniston JT Enyedi A 《The Journal of biological chemistry》2002,277(39):36146-36151
The role of the plasma membrane Ca(2+) pump (PMCA) is to remove excess Ca(2+) from the cytosol to maintain low intracellular Ca(2+) levels. Asp(1080) lies within an acidic sequence between the C-terminal inhibitory region and the catalytic core of PMCAs and is part of the caspase-3 recognition site of isoform 4b. Caspase-3 cuts immediately after this residue and activates the pump by removing the inhibitory region (Pászty, K., Verma, A. K., Padányi, R., Filoteo, A. G., Penniston, J. T., and Enyedi, A. (2002) J. Biol. Chem. 277, 6822-6829). Asp(1080) had not been believed to have any other role, but here we show that it also plays a critical role in the autoinhibition and calmodulin activation of PMCA4b. Site-specific mutation of Asp(1080) to Asn, Ala, or Lys in PMCA4b resulted in a substantial increase in the basal activity in the absence of calmodulin. All Asp(1080) mutants exhibited an increased affinity for calmodulin because of an increase in the rate of activation by calmodulin. This rate was higher when the inhibition was weaker, showing that a strong inhibitory interaction slows the activation rate. In contrast, mutating the nearby Asp(1077) had no effect on basal activity or calmodulin activation. We propose that the conserved Asp(1080), even though it is neither in the regulatory domain nor in the catalytic core, plays an essential role in inhibition by stabilizing the inhibited state of the enzyme. 相似文献
84.
The inhibitory activity of natural products on plant p-hydroxyphenylpyruvate dioxygenase 总被引:3,自引:0,他引:3
Meazza G Scheffler BE Tellez MR Rimando AM Romagni JG Duke SO Nanayakkara D Khan IA Abourashed EA Dayan FE 《Phytochemistry》2002,60(3):281-288
The inhibitory activity of 34 natural products of various structural classes on hydroxyphenylpyruvate dioxygenase (HPPD), the target site for triketone herbicides, and the mode of interaction of selected natural products were investigated. Recombinant HPPD from arabidopsis is sensitive to several classes of natural compounds including, in decreasing order of sensitivity, triketones, benzoquinones, naphthoquinones and anthraquinones. The triketone natural products acted as competitive tight-binding inhibitors, whereas the benzoquinones and naphthoquinones did not appear to bind tightly to HPPD. While these natural products may not have optimal structural features required for in vivo herbicidal activity, the differences in their kinetic behavior suggest that novel classes of HPPD inhibitors may be developed based on their structural backbones. 相似文献
85.
86.
Human DNA polymerase mu (Pol mu) exhibits an unusual replication slippage ability at AAF lesion 下载免费PDF全文
We analyzed the ability of various cell extracts to extend a radiolabeled primer past an N-2-acetylaminofluorene (AAF) adduct located on a primed single-stranded template. When the 3′ end of the primer is located opposite the lesion, partially fractionated human primary fibroblast extracts efficiently catalyzed primer-terminus extension by adding a ladder of about 15 dGMPs, in an apparently non-templated reaction. This activity was not detected in SV40-transformed fibroblasts or in HeLa cell extracts unless purified human DNA polymerase mu (Pol µ) was added. In contrast, purified human Pol µ alone could only add three dGMPs as predicted from the sequence of the template. These results suggest that a cofactor(s) present in cellular extracts modifies Pol µ activity. The production of the dGMP ladder at the primer terminus located opposite the AAF adduct reveals an unusual ability of Pol µ (in conjunction with its cofactor) to perform DNA synthesis from a slipped intermediate containing several unpaired bases. 相似文献
87.
Two types of males are present in the Jalapa population of Xiphophorus helleri: Males with a black or dark brownish mid-lateral stripe ("black males") mature earlier and are smaller than males with a red or brownish mid-lateral stripe ("red males"). We tested the hypothesis that the colour patterns of red males may be regarded as ornaments, which evolved as the result of inter- and/or intrasexual selection. As predicted, in choice tests females exhibited a strong preference for red versus black males. Furthermore, in competition experiments red males became dominant over black males with no exception, both when body size was equal and even when red males were 3–5 mm smaller than black males. However, contrary to our prediction, sneak–chase behaviour in black males was not detected, and courtship displays occurred at similar rates in both morphs. Red males are always heterozygous, with one allele for red and another for black colouration. This genetic constraint potentially prevents the extinction of the black morph. Possibly, the colour patterns of red males are functioning as indicators of heterozygosity. According to the "heterozygosity theory of mate choice", the female's preference for red males may be adaptive. 相似文献
88.
Novel derivatives of 9,10-anthraquinone are selective algicides against the musty-odor cyanobacterium Oscillatoria perornata 总被引:2,自引:0,他引:2
Schrader KK Nanayakkara NP Tucker CS Rimando AM Ganzera M Schaneberg BT 《Applied and environmental microbiology》2003,69(9):5319-5327
Musty "off-flavor" in pond-cultured channel catfish (Ictalurus punctatus) costs the catfish production industry in the United States at least 30 million US dollars annually. The cyanobacterium Oscillatoria perornata (Skuja) is credited with being the major cause of musty off-flavor in farm-raised catfish in Mississippi. The herbicides diuron and copper sulfate, currently used by catfish producers as algicides to help mitigate musty off-flavor problems, have several drawbacks, including broad-spectrum toxicity towards the entire phytoplankton community that can lead to water quality deterioration and subsequent fish death. By use of microtiter plate bioassays, a novel group of compounds derived from the natural compound 9,10-anthraquinone have been found to be much more selectively toxic towards O. perornata than diuron and copper sulfate. In efficacy studies using limnocorrals placed in catfish production ponds, application rates of 0.3 micro M (125 micro g/liter) of the most promising anthraquinone derivative, 2-[methylamino-N-(1'-methylethyl)]-9,10-anthraquinone monophosphate (anthraquinone-59), dramatically reduced the abundance of O. perornata and levels of 2-methylisoborneol, the musty compound produced by O. perornata. The abundance of green algae and diatoms increased dramatically 2 days after application of a 0.3 micro M concentration of anthraquinone-59 to pond water within the limnocorrals. The half-life of anthraquinone-59 in pond water was determined to be 19 h, making it much less persistent than diuron. Anthraquinone-59 appears to be promising for use as a selective algicide in catfish aquaculture. 相似文献
89.
Ostafin AE Ponomarenko NS Popova JA Jäger M Bylina EJ Norris JR 《Photosynthesis research》2003,77(1):53-68
The utility of photosynthetically defective mutants in the purple photosynthetic bacterium Blastochloris viridis (formerly Rhodopseudomonas viridis)was demonstrated with construction of a reaction-center deficient mutant, LH 1-H. This LH 1-H mutant has a photosynthetic
apparatus in which most of the puf operon genes were deleted, resulting in an organism containing only the genes for the light harvesting polypeptides and the
H subunit of the reaction center. This B. viridisstrain containing a truncation of the puf operon was characterized by gel electrophoresis, lipid-to-protein ratio analysis, optical spectroscopy, electron paramagnetic
resonance and transmission electron microscopy. Optical and electron paramagnetic resonance spectroscopies revealed no photoactivity
in this LH 1-H mutant consistent with the absence of intact reaction centers. Electron paramagnetic resonance evidence for
assembled LH 1 complexes suggested that the interactions between light harvesting polypeptide complexes in membranes were
largely unchanged despite the absence of their companion reaction center cores. The observed increase in the lipid-to-protein
ratio was consistent with modified interactions between LH 1s, a view supported by transmission electron microscopy analysis
of membrane fragments. The results show that B. viridis can serve as a practical system for investigating structure-function relationships in membranes and photosynthesis through
the construction of photosynthetically defective mutants.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
90.
A novel method for the covalent attachment of erythrocytes to glass microscope coverslips that can be used to image intact
cells and the cytoplasmic side of the cell membrane with either solid or liquid mode atomic force microscopy (AFM) is described.
The strong binding of cells to the glass surface is achieved by the interaction of cell membrane carbohydrates to lectin,
which is bound to N-5-azido-2-nitrobenzoyloxysuccinimide (ANBNOS)-coated coverslips (1). The effectiveness of this method
is compared with the other commonly used methods of immobilizing intact erythrocytes on glass coverslips for AFM observations.
Experimental conditions of AFM imaging of biologic tissue are discussed, and typical topographies of the extracellular and
the cytoplasmic surfaces of the plasma membrane in the dry state and in the liquid state are presented. Comparison of the
spectrin network of cell age-separated erythrocytes has demonstrated significant loss in the network order in older erythrocytes.
The changes are quantitatively described using the pixel height histogram and window size grain analysis. 相似文献