Oxidative phosphorylation in a yeast mutant lacking α-ketoglutarate dehydrogenase activity

The effect of α-ketoglutarate deficiency on the oxidative phosphorylation in yeast mitochondria was studied. By determining the properties of electron transport and energy transduction systems of mutant mitochondria it was found that the lack of α-ketoglutarate dehydrogenase activity in mitochondria does not result in any functional defect in the oxidative phosphorylation system.     

Immunochemical analysis of the membrane proteins of rat liver and Zajdela hepatoma mitochondria

The contents of mitochondrial inner membrane protein complexes were compared in normal liver and in Zajdela hepatoma mitochondria by the immunotransfer technique. Antibodies against core proteins 1 and 2, cytochrome c1, the iron-sulfur protein of Complex III, subunits I and II of cytochrome oxidase, and the alpha and beta subunits of the F1-ATPase were used. In addition, antibodies against a primary dehydrogenase, beta-hydroxybutyrate dehydrogenase, as well as the outer membrane pore protein were used. The results indicate that the components of the cytochrome chain and porin are greatly enriched in hepatoma mitochondria compared to normal rat liver mitochondria. This enrichment was also reflected in the rates of respiration in tumor mitochondria using a variety of substrates. Enrichment of porin may partially account for increased hexokinase binding to tumor mitochondria. In contrast to the respiratory chain components, the F1-ATPase and F0 (measured by DCCD binding) were not increased in tumor mitochondria. Thus, Zajdela hepatoma mitochondria components are nonstoichiometric, being enriched in oxidative capacity but relatively deficient in ATP synthesizing capacity. Finally, beta-hydroxybutyrate dehydrogenase, which is often decreased in hepatoma mitochondria, was shown here by immunological methods to be decreased by only 40%, whereas enzyme activity was less than 5% of that in normal rat liver.     

Genetic determination of the mitochondrial adenine nucleotide translocation system and ITS role in the eukaryotic cell

On integrating experimental data published previously, the following picture of the mitochondrial adenine nucleotide (AdN) translocation system is being presented: 1. The AdN translocation system serves not only to transport ATP synthesized within mitochondria into the cytosol but also to transport cytosolic ATP into the mitochondria when oxidative phosphorylation is not functioning. 2. The AdN translocator is coded for by nuclear genes and the mitochondrial protein synthesis is not involved in its formation. 3. The AdN translocation system must be preserved and functioning even in cells which could dispense with oxidative phosphorylation. It assures appropriate concentrations of intramitochondrial ATP. 4. The intramitochondrial ATP is required for normal replication of mitochondrial DNA. Tis supports the view that the mitochondrion is a self-replicating semi-autonomous organelle. 5. The appropriate concentration of ATP must be present in mitochondria to make possible cell growth or multiplication. This points to a direct or indirect role of mitochondria in the control of cell proliferation.     

Yeast ADP/ATP carrier (AAC) proteins exhibit similar enzymatic properties but their deletion produces different phenotypes.

Saccharomyces cerevisiae strains expressing a single type of ADP/ATP carrier (AAC) protein were prepared from a mutant in which all AAC genes were disrupted, by transformation with plasmids containing a chosen AAC gene. As demonstrated by measurements of [14C]ADP specific binding and transport, all three translocator proteins, AAC1, AAC2 and AAC3 when present in the mitochondrial membrane, exhibited similar translocation properties. The disruption of some AAC genes, however, resulted in phenotypes indicating that the function of these proteins in whole cells can be quite different. Specifically, we found that the disruption of AAC1 gene, but not AAC2 and AAC3, resulted in a change in colony phenotype.     

A third ADP/ATP translocator gene in yeast

The op1 mutation in yeast is known to be due to a defect in the mitochondrial ADP/ATP translocator. Sequencing of the gene AAC2 revealed that the mutation resulted from a single base change that caused a replacement of arginine 97 by a histidine. The gene encoding AAC2 was also cloned and sequenced from an op1 revertant capable of growth on glycerol as a sole carbon source. Sequence analysis indicates that the reverted gene underwent rearrangement in which a portion of an unknown gene was used to repair the mutation. An oligonucleotide complementary to this insert was used to clone a previously unrecognized gene encoding ADP/ATP translocator in yeast. The newly discovered gene, AAC3, is homologous with the previously known genes AAC1 and AAC2. Gene disruption experiments suggest that AAC2 encodes the majority of the translocator. Expression of AAC1 and AAC2 required derepressed conditions whereas expression of AAC3 occurred almost exclusively under anaerobic conditions. Both the op1 mutant and the strain that contains an interrupted AAC2 were able to grow under anaerobic conditions, suggesting that AAC3 can replace the gene product of AAC2. Indeed, when cloned into multicopy plasmid, AAC3 was able to replace the disrupted AAC2 in the JLY-73 strain. The concomitant disruption of the AAC2 and AAC3, however, results in arrest of cell growth under conditions of low oxygen tension. The discovery of a third gene encoding ADP/ATP translocator helps to clarify certain characteristics of op1 mutants which could not be resolved in the past.     

A new species of the genus Seticornuta Morley (Hymenoptera,Ichneumonidae, Metopiinae) from South Korea

Old World species of the genus Seticornuta Morley are reviewed. Seven species of this genus were recorded worldwide, but only one species, Seticornuta albopilosa (Cameron), was known from the Old World. Here, we report one new species, Seticornuta koreana sp. n., from South Korea, and redescribe the other known Old World species, Seticornuta albopilosa, with photographs.     

A new species of Cymodusa Holmgren, 1859 (Hymenoptera: Ichneumonidae: Campopleginae) from Turkey

Cymodusa (Cymodusa) propodeata sp. n. from Turkey is described and illustrated. It is distinguished from the similar C. (s. str.) oculator Dbar, 1985 by moderately narrowed head behind eyes, developed clypeal fovea, area superomedia not separated by carina from basal and petiolar area and coloration of the body.     

不受欢迎的生物多样性：香港的外来植物物种

香港早在19世纪中叶开始就有外来植物入侵的记录,迄今为止,已发现多达238种已归化的外来或怀疑为外来的植物,其中又以薇甘菊（Mikania micrantha)、五爪金龙（Ipomoea cairica)、假臭草（Eupatorium catarium)、大黍（Panicum maximum)等最常见,外来植物最常见于受人为干扰的生境,例如荒废农田及路旁等,而较少在天然林地生境及贫瘠的灌草丛中发现,外来植物的对本地生态系统的影响主要局限于低地生境,它们常形成单优种群,减少了生境及贫瘠的灌草丛中发现,外来植物对本地生态系统的影响主要局限于低地生境,它们常形成单优种群,减少少了生境及动植物的多样性,外来动物对香港原生植物影响最大的是于20世纪70年代入侵的松树线虫（Bur-saphelenchus xylophilus)。外来的脊椎动物也有可能对香港的植物被演替产生影响,目前香港的外来植物当中,有些在大陆较少分布或没有记录,作为华南最大的港口,香港对外来物种的引入扮演着重要的角色,因此制定控制外来种在香港及华南地区的引入及传播的政策及措施非常重要。