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991.
Two heterotrophic members of the Dictyochophyceae (stramenopiles), Pteridomonas danica and Ciliophrys infusionum, were investigated. An undescribed organelle bounded by four membranes and closely associated with the nucleus was detected in P. danica. The outermost membrane was continuous with the outer nuclear membrane. These features strongly suggested that this organelle was a vestigial chloroplast. A photosynthetic gene, rbcL, was successfully amplified by polymerase chain reaction (PCR) from P. danica and C. infusionum. These sequences were readily and well aligned with those of photosynthetic stramenopiles. Phylogenetic trees of 18S rDNA and rbcL were constructed. In all the trees obtained, P. danica and C. infusionum appeared in two different clades, the Pedinellales clade and the Ciliophryales/Rhizochromulinales clade, each of which contained photosynthetic members as well as heterotrophic members. The results indicated that the loss of photosynthetic ability occurred independently in P. danica and C. infusionum. This is the first report of the presence of a vestigial chloroplast (leucoplast) in colorless dictyochophytes. 相似文献
992.
993.
Mitsuhiro Ueda Miki Kojima Tomoye Yoshikawa Norio Mitsuda Keiichi Araki Takashi Kawaguchi Kazutaka Miyatake Motoo Arai Tamo Fukamizo 《European journal of biochemistry》2003,270(11):2513-2520
A family 19 chitinase gene from Aeromonas sp. No.10S-24 was cloned, sequenced, and expressed in Escherichia coli. From the deduced amino acid sequence, the enzyme was found to possess two repeated N-terminal chitin-binding domains, which are separated by two proline-threonine rich linkers. The calculated molecular mass was 70 391 Da. The catalytic domain is homologous to those of plant family 19 chitinases by about 47%. The enzyme produced alpha-anomer by hydrolyzing beta-1,4-glycosidic linkage of the substrate, indicating that the enzyme catalyzes the hydrolysis through an inverting mechanism. When N-acetylglucosamine hexasaccharide [(GlcNAc)6] was hydrolyzed by the chitinase, the second glycosidic linkage from the nonreducing end was predominantly split producing (GlcNAc)2 and (GlcNAc)4. The evidence from this work suggested that the subsite structure of the enzyme was (-2)(-1)(+1)(+2)(+3)(+4), whereas most of plant family 19 chitinases have a subsite structure (-3)(-2)(-1)(+1)(+2)(+3). Thus, the Aeromonas enzyme was found to be a novel type of family 19 chitinase in its structural and functional properties. 相似文献
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997.
Summary We investigated whether lysine transport would be subject to adaptive regulation in Caco-2 human intestinal cells. The activity of Lys transport in Caco-2 cells decreased with increasing incubation time with lOmM Lys. Among the two systems involved in Lys transport, the system b0,+ component was greatly decreased by incubating cells ith lOmM Lys, whereas the system y+ component did not change. These results suggest that system b0,+ mainly contributes to the adaptive regulation of Lys transport in Caco-2 cells. 相似文献
998.
999.
The Effects of GA3 on Weeping of Growing Shoots of the Japanese Cherry, Prunus spachiana 总被引:2,自引:0,他引:2
Nakamura Teruko; Saotome Maki; Ishiguro Yukiko; Itoh Reiko; Higurashi Sachiko; Hosono Mayumi; Ishii Yukio 《Plant & cell physiology》1994,35(3):523-527
The effects of GA3 on weeping were examined in the Japanesecherry, Prunus spachiana. Current-year branches first elongateupward then gradually bend to elongate downward. GA3 appliedto apical buds promoted the upward elongation and inhibitedthe bending. Thus, GA3 changed the direction of branches duringtheir growth. (Received April 12, 1993; Accepted February 2, 1994) 相似文献
1000.