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71.
I L Sun R Garcia-Ca?ero W Liu W Toole-Simms F L Crane D J Morré H L?w 《Biochemical and biophysical research communications》1987,145(1):467-473
Proton release from HeLa cells is stimulated by external oxidants for the transplasmalemma electron transport enzymes. These oxidants, such as ferricyanide and diferric transferrin, also stimulate cell growth. We now present evidence that proton release associated with the reduction of ferricyanide and diferric transferrin is through the Na+/H+ antiport. The stoichiometry of H+/e- release with diferric transferrin is over 50 to 1, which is greater than expected for oxidation of a protonated transmembrane electron carrier. Diferric transferrin induced proton release depends on external sodium and is inhibited by amiloride. Proton release is also inhibited when diferric transferrin reduction is inhibited by apotransferrin. A tightly coupled association between the redox system and the antiport is shown by sodium dependence and amiloride inhibition of diferric transferrin reduction. The results indicate a new role for ferric transferrin in growth stimulation by activation of the sodium-proton antiport. 相似文献
72.
L Sun G Serrero A Piltch J Hayashi 《Biochemical and biophysical research communications》1987,148(2):603-608
Thymic endocrine epithelial cell line TEA3A1 can be maintained and passaged in a serum-free WAJC404A medium supplemented with insulin, transferrin, dexamethasone and EGF. EGF not only promotes the growth of these cells but also regulates the activation of phospholipase A2 enzyme activity. The binding of [125I]EGF to the TEA3A1 cells is temperature and time dependent, saturable and can be blocked by excess unlabelled EGF. Two classes of EGF receptors are found on these cells. One with Kd of 5 X 10(-11)M (approximately 3000 sites/cell) and the other with Kd of 5 X 10(-9)M (approximately 30,000 sites/cell). The resynthesis of EGF receptor in TEA3A1 cells after down-regulation requires about 24 hrs and can be blocked by both actinomycin D and cycloheximide. 相似文献
73.
74.
Effects of preillumination on photophobic response (light-adaptation) and recovery of the photophobic sensitivity in the dark (dark-adaptation) in Stentor coeruleus were examined. When the cells were preilluminated with white light of 7.80 W/m2 for 2 min, the fluence-rate response curve of photophobic response was shifted toward higher light intensities by half an order of magnitude compared to the one without preillumination. Preillumination with a higher light intensity resulted in a further shift of the fluencerate response curve. An action spectrum for light-adaptation showed a primary peak at 610 nm and secondary peaks at 540 and 480 nm which are almost identical to the peaks observed in the photophobic action spectrum.The light-adapted cells showed a recovery of their photophobic sensing ability following dark treatment. Dark-adaptation resulted in total recovery of photophobic sensing ability in 8 minutes for the most cases examined. 相似文献
75.
76.
Junzou Hiratsuka Hiroaki Shimada Robert Whittier Takashi Ishibashi Masahiro Sakamoto Masao Mori Chihiro Kondo Yasuko Honji Chong-Rong Sun Bing-Yuan Meng Yu-Qing Li Akira Kanno Yoko Nishizawa Atsushi Hirai Kazuo Shinozaki Masahiro Sugiura 《Molecular & general genetics : MGG》1989,217(2-3):185-194
Summary The entire chloroplast genome of the monocot rice (Oryza sativa) has been sequenced and comprises 134525 bp. Predicted genes have been identified along with open reading frames (ORFs) conserved
between rice and the previously sequenced chloroplast genomes, a dicot, tobacco (Nicotiana tabacum), and a liverwort (Marchantia polymorpha). The same complement of 30 tRNA and 4 rRNA genes has been conserved between rice and tobacco. Most ORFs extensively conserved
betweenN. tabacum andM. polymorpha are also conserved intact in rice. However, several such ORFs are entirely absent in rice, or present only in severely truncated
form. Structural changes are also apparent in the genome relative to tobacco. The inverted repeats, characteristic of chloroplast
genome structure, have expanded outward to include several genes present only once per genome in tobacco and liverwort and
the large single copy region has undergone a series of inversions which predate the divergence of the cereals. A chimeric
tRNA pseudogene overlaps an apparent endpoint of the largest inversion, and a model invoking illegitimate recombination between
tRNA genes is proposed which accounts simultaneously for the origin of this pseudogene, the large inversion and the creation
of repeated sequences near the inversion endpoints. 相似文献
77.
Summary The Bacillus subtilis cdd gene encoding cytidine/2-deoxycytidine deaminase has been located by transduction at approximately 225 degrees on the chromosome, and the gene order rpC-lys-cdd-aroD was established. The gene was isolated from a library of B. subtilis DNA cloned in D69 by complementation of an Escherichia coli cdd mutation. Minicell experiments revealed a molecular mass of 14000 dalton for the cytidine deaminase subunit encoded by the cloned DNA fragment. The molecular weight of the native enzyme was determined to be 58000, suggesting that it consists of four identical subunits. The nucleotide sequence of 1170 bp, including the cdd gene, was determined. An open reading frame encoding a polypeptide with a calculated molecular mass of 14800 dalton was deduced to be the coding region for cdd. The deduced amino acid composition of the 136-amino acid-long subunit shows that it contains six cysteine residues. A computer search in the GenBank DNA sequence library revealed that the 476 bp HindIII fragment containing the putative promoter region and the first ten codons of cdd is identical to the P43 promoter-containing fragment previously isolated by Wang and Doi (1984). They showed that the fragment contained overlapping promoters transcribed by B. subtilis 43 and 37 RNA polymerase holoenzymes during growth and stationary phase.Abbreviations SDS
sodium dodecyl sulphate
- Ap
ampicillin resistance
- Tetr
tetracycline resistance
- Kmr
kanamycin resistance 相似文献
78.
79.
Maria C. Nieto Elizabeth S. Song Denise McKinney Minnie McMillan Robert S. Goodenow 《Immunogenetics》1989,30(5):361-369
We have analyzed changes in the antigenicity of major histocompatibility complex class I molecules resulting from the association
of human beta-2 micro-globulin (B2m) with the mouse class I heavy chain. In particular, the H-2Ld molecule exhibited enhanced crossreactivity for the 34-1-2 monoclonal antibody. In order to assess the nature of this structural
alteration induced by human B2m, we utilized H-2 class I hybrid molecules in the mapping of the 34-1-2 determinant to the
helical region of the alpha-1 domain. H-2Ld class I hybrid molecules were then used to establish the importance of the alpha-2 and- 3 domains in the observed increase
of 34-1-2 cross-reactivity following exchange with human B2m. The H-2Ld hybrids suggest that alterations in interdomain contact are responsible for enhanced 34-1-2 cross-reactivity on the H-2Ld molecule. It is likely that this alteration arises through changes in class I conformation at regions of the molecule distant
from points of contact between B2m and the class I molecule. This suggests that perturbations induced by association of human
B2m with H-2Ld can affect the conformation of the alpha-1 and- 2 superdomain. That class I antigenic determinants are altered by the association
of human B2m with mouse class I further suggests that the class I molecule is structurally flexible and may reflect the ability
of the class I molecule to bind and present a vast array of disparate peptides to the T-cell receptor. 相似文献
80.
通过细胞学观察,在普通小麦栽培品种“丰抗13”和“京红1号”的杂交后代中,发现有多价体出现,这就表明有染色体易位发生。为进一步弄清究竟是哪条染色体发生了易位,我们采用单体测交方法,观察鉴定所有各单体系F_1的花粉母细胞第一次减数分裂中期Ⅰ(以下简称PMCs中Ⅰ)染色体构型。从鉴定结果发现,凡2n=42的F_1 PMCs中Ⅰ出现19~Ⅱ 1~Ⅳ,而2n=41的F_1PMCs中Ⅰ的染色体构型不同,单体与易位有关的两个单体系4B和1D F_1 PMCs中的Ⅰ构型中有部分呈现为19个二价体加1个三价体,即19~Ⅱ 1~Ⅲ,没有单价体,而其余各单体系F_1 PMCs中Ⅰ构型则表现为18个二价体,1个四价体和1个单价体,即18~Ⅱ 1~Ⅰ 1~Ⅳ。因此,可以肯定“丰抗13”存在1个染色体易位,其有关染色体就是4B和1D。 相似文献