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71.
Mary T. Doan Michael D. Neinast Erika L. Varner Kenneth C. Bedi David Bartee Helen Jiang Sophie Trefely Peining Xu Jay P. Singh Cholsoon Jang J. Eduardo Rame Donita C. Brady Jordan L. Meier Kenneth B. Marguiles Zoltan Arany Nathaniel W. Snyder 《Journal of lipid research》2022,63(6):100224
Anabolic metabolism of carbon in mammals is mediated via the one- and two-carbon carriers S-adenosyl methionine and acetyl-coenzyme A. In contrast, anabolic metabolism of three-carbon units via propionate has not been shown to extensively occur. Mammals are primarily thought to oxidize the three-carbon short chain fatty acid propionate by shunting propionyl-CoA to succinyl-CoA for entry into the TCA cycle. Here, we found that this may not be absolute as, in mammals, one nonoxidative fate of propionyl-CoA is to condense to two three-carbon units into a six-carbon trans-2-methyl-2-pentenoyl-CoA (2M2PE-CoA). We confirmed this reaction pathway using purified protein extracts provided limited substrates and verified the product via LC-MS using a synthetic standard. In whole-body in vivo stable isotope tracing following infusion of 13C-labeled valine at steady state, 2M2PE-CoA was found to form via propionyl-CoA in multiple murine tissues, including heart, kidney, and to a lesser degree, in brown adipose tissue, liver, and tibialis anterior muscle. Using ex vivo isotope tracing, we found that 2M2PE-CoA also formed in human myocardial tissue incubated with propionate to a limited extent. While the complete enzymology of this pathway remains to be elucidated, these results confirm the in vivo existence of at least one anabolic three- to six-carbon reaction conserved in humans and mice that utilizes propionate. 相似文献
72.
K. Yoshikawa 《Journal of biological physics》2002,28(4):701-712
The mechanism of the self-regulation of gene expression in living cells is generally explained by considering complicated networks of key-lock relationships, and in fact there is a large body of evidence on a hugenumber of key-lock relationships. However, in the present article we stress that with the network hypothesis alone it is impossible to fully explain the mechanism of self-regulation in life. Recently, it has been established that individual giant DNA molecules, larger than several tens of kilo base pairs, undergo a large discrete transition in their higher-order structure. It has become clear that nonspecific weak interactions with various chemicals, suchas polyamines, small salts, ATP and RNA, cause on/off switching in the higher-order structure of DNA. Thus, the field parameters of the cellular environment should play important roles in the mechanism of self-regulation, in addition to networks of key and locks. This conformational transition induced by field parameters may be related to rigid on/off regulation, whereas key-lock relationships may be involved in a more flexible control of gene expression. 相似文献
73.
74.
Katsuhiko Kamada Daniela Barillà 《BioEssays : news and reviews in molecular, cellular and developmental biology》2018,40(2)
Genome maintenance requires various nucleoid‐associated factors in prokaryotes. Among them, the SMC (Structural Maintenance of Chromosomes) protein has been thought to play a static role in the organization and segregation of the chromosome during cell division. However, recent studies have shown that the bacterial SMC is required to align left and right arms of the emerging chromosome and that the protein dynamically travels from origin to Ter region. A rod form of the SMC complex mediates DNA bridging and has been recognized as a machinery responsible for DNA loop extrusion, like eukaryotic condensin or cohesin complexes, which act as chromosome organizers. Attention is now turning to how the prototype of the complex is loaded on the entry site and translocated on chromosomal DNA, explaining its overall conformational changes at atomic levels. Here, we review and highlight recent findings concerning the prokaryotic SMC complex and discuss possible mechanisms from the viewpoint of protein architecture. 相似文献
75.
76.
Recovery of transgenic rice plants expressing the rice dwarf virus outer coat protein gene (S8) 总被引:3,自引:0,他引:3
H. H. Zheng Y. Li Z. H. Yu W. Li M. Y. Chen X. T. Ming R. Casper Z. L. Chen 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,94(3-4):522-527
The coding region of the eighth largest segment (S8) of the rice dwarf virus (RDV) was obtained from a RDV Fujian isolate.
It was then cloned into pTrcHisA for expression in E. coli and into vector pE3 for plant transformation. By using callus derived from mature rice embryos as the target tissue, we obtained
regenerated rice plants after bombardment of the former with plasmid pE3R8 containing the RDV S8 gene and the marker gene
neomycin phosphotransferase (NPT II). Southern blotting confirmed the integration of the RDV S8 gene into the rice genome.
The expression of the outer coat protein in both E. coli and rice plants was confirmed by western blotting. The recovery of transgenic rice plants expressing S8 gene is an important
step towards studying the function of the RDV genes and obtaining RDV-resistant rice plants.
Received: 1 March 1996 / Accepted: 2 August 1996 相似文献
77.
Shinya Yoshikawa Chikako Nagasato Terunobu Ichimura Taizo Motomura 《Phycological Research》2003,51(2):77-82
Morphological changes and chromatin condensation of sperm nuclei were observed during spermatogenesis in the fucalean brown alga Cystoseira hakodatensis (Yendo) Fensholt. Ultrastructural studies have shown that the mature spermatozoid has an elongated and concave nucleus with condensed chromatin. The morphological changes and the chromatin condensation process during spermatogenesis was observed. Nuclear size decreased in two stages during spermatogenesis. During the first stage, spherical nuclei decreased in size as they were undergoing meiotic divisions and the subsequent mitoses within the antheridium. During the second stage, the morphological transformation from a spherical into an elongated nucleus occurred. Afterwards, chromatin condensed at the periphery in each nucleus, and chromatin‐free regions were observed in the center of the nucleus. These chromatin‐free regions in the center of nucleus were compressed by the peripheral chromatin‐condensed region. As the result, the elongated and concave nucleus of the mature sperm consisted of uniformly well‐condensed chromatin. 相似文献
78.
Valery Andrushchenko Zoya Leonenko David Cramb Hans van de Sande Hal Wieser 《Biopolymers》2002,61(4):243-260
The interaction of natural calf thymus DNA with Cr3+ ions was studied at room temperature by means of vibrational CD (VCD) and infrared absorption (ir) spectroscopy, and atomic force microscopy (AFM). Cr3+ ion binding mainly to N7 (G) and to phosphate groups was demonstrated. ψ‐Type VCD spectra resembling electronic CD (ECD) spectra, which appear during ψ‐type DNA condensation, were observed. These spectra are characterized mainly by an anomalous, severalfold increase of VCD intensity. Such anomalous VCD spectra were assigned to DNA condensation with formation of large and dense particles of a size comparable to the wavelength of the probing ir beam and possessing large‐scale helicity. Atomic force microscopy confirmed DNA condensation by Cr3+ ions and the formation of tight DNA particles responsible for the ψ‐type VCD spectra. Upon increasing the Cr3+ ion concentration the shape of the condensates changed from loose flower‐like structures to highly packed dense spheres. No DNA denaturation was seen even at the highest concentration of Cr3+ ions studied. The secondary structure of DNA remained in a B‐form before and after the condensation. VCD and ir as well as AFM proved to be an effective combination for investigating DNA condensation. In addition to the ability of VCD to determine DNA condensation, VCD and ir can in the same experiment provide unambiguous information about the secondary structure of DNA contained in the condensed particles. © 2002 Wiley Periodicals, Inc. Biopolymers 61: 243–260, 2002 相似文献
79.
We describe here the chemical induction of premature condensed chromosomes in human peripheral lymphocytes after culture for 6 h. Many have attempted this induction without culture or with short-term culture, because this technique permits prompt cytogenetic biodosimetry of radiation accidents. Lymphocytes were separated from blood, incubated in the presence of phytohemagglutinin, ATP, and p34cdc2/cyclin B kinase, then treated with calyculin A during the last hour. The culture medium was supplemented with a lower concentration of fetal calf serum than conventionally used to minimize its possible interference with the effects of these drugs. We obtained, rarely, a suitable morphology of premature chromosome condensation in short-term cultured lymphocytes for conventional chromosome aberration analysis. 相似文献
80.
Chinese hamster ovary (CHO) cells were treated with ultraviolet radiation or the alkylating agents, nitrogen mustard or trenimon, and chromosome damage to G2 phase cells were scored by the premature chromosome condensation (PCC) method or the metotic chromosome method. Treatment with these agents produced gaps but not chromatid breaks or exchanges. After UV treatment, the gap frequency observed in G2-PCC was higher than in the mitotic chromosomes, while the reverse trend was observed after treatment with nitrogen mustard or trenimon. These results suggest that two types of chromosome gaps exist, both of which are observable in mitotic chromosomes while only one type is observable in PCC due to differences in the stages of condensation between PCC and mitotic chromosomes. 相似文献