Distribution and prevalence of the predatory planarian Artioposthia triangulata (Dendy) (Trieladida: Terricola) in Scotland

The distribution of the New Zealand flatworm (Artioposthia triangulata) in Scotland was surveyed between July 1991 and February 1993. There were 348 records from domestic gardens, 56 from botanic gardens, garden centres and nurseries, with only 13 from farms. Although most of the records came from around the major cities the flatworm was found to have become established throughout the Scottish mainland and some of the Islands, e.g. Bute, Gigha, Orkney and Skye. The impact of the flatworm on earthworm populations in agricultural land in Scotland was, as yet, found to be minimal but the fact that seven adjacent farms near Dunoon were infected suggested it could be spread from farm to farm and that in the West of Scotland it could become widespread in agricultural land.     

PrrC, a Sco homologue from Rhodobacter sphaeroides, possesses thiol-disulfide oxidoreductase activity

PrrC is a Sco homologue in Rhodobacter sphaeroides that is associated with PrrBA, a two-component signal transduction system that induces photosynthesis gene expression in response to a decrease in oxygen tension. Although Sco proteins have been shown to bind copper the observation that they are structurally-related to thioredoxins suggested that they might possess thiol-disulfide oxidoreductase activity. Our results show that PrrC reduces Cu(2+) to Cu(+) and possesses disulfide reductase activity. These results indicate that some bacterial Sco proteins may have biochemical properties that are distinct from those of mitochondrial Sco proteins.     

超高产水稻剑叶衰老过程中PSⅡ激发压与 Rubisco大、小亚基含量的相关性

研究了大田生长条件下两系超高产杂交水稻(Oryza sati va L.)"两优培九"和我国大面积推广的三系杂交水稻"汕优63"从灌浆期到收获期剑叶PSⅡ光化学特性和Rubjsco大、小亚基含量的变化.结果表明:可溶性蛋白质和叶绿素含量随剑叶生长时间的延长先缓慢下降,后期有一个快速降解的过程,"汕优63"降解的速率高于"两优培九";Fv/Fm和qP都呈下降的趋势,qN则是先降然后上升.激发压(1 qP)在前期的变化较为平稳,后期则急剧增加,"汕优63"较"两优培九"增加快.Rubi Sco大、小亚基的含量与叶绿素、可溶性蛋白含量一样在前期下降比较慢,后期也有一个快速降解的过程,"汕优63"比"两优培九"降解快.激发压的增加与Rubisco大、小亚基的降解呈显著的线性相关性.我们推测PSⅡ激发压的急剧增加可能诱发了水稻剑叶的快速衰老过程."两优培九"高产的重要生理原因之,可能是它比"汕优63"有更强的光合能力并能维持更持久和较高的光合功能期.     

Cox17 Protein Is an Auxiliary Factor Involved in the Control of the Mitochondrial Contact Site and Cristae Organizing System

The mitochondrial contact site and cristae organizing system (MICOS) is a recently discovered protein complex that is crucial for establishing and maintaining the proper inner membrane architecture and contacts with the outer membrane of mitochondria. The ways in which the MICOS complex is assembled and its integrity is regulated remain elusive. Here, we report a direct link between Cox17, a protein involved in the assembly of cytochrome c oxidase, and the MICOS complex. Cox17 interacts with Mic60, thereby modulating MICOS complex integrity. This interaction does not involve Sco1, a partner of Cox17 in transferring copper ions to cytochrome c oxidase. However, the Cox17-MICOS interaction is regulated by copper ions. We propose that Cox17 is a newly identified factor involved in maintaining the architecture of the MICOS complex.     

Crystal structure of yeast Sco1

The Sco family of proteins are involved in the assembly of the dinuclear Cu_A site in cytochrome c oxidase (COX), the terminal enzyme in aerobic respiration. These proteins, which are found in both eukaryotes and prokaryotes, are characterized by a conserved CXXXC sequence motif that binds copper ions and that has also been proposed to perform a thiol:disulfide oxidoreductase function. The crystal structures of Saccharomyces cerevisiae apo Sco1 (apo-ySco1) and Sco1 in the presence of copper ions (Cu–ySco1) were determined to 1.8- and 2.3-Å resolutions, respectively. Yeast Sco1 exhibits a thioredoxin-like fold, similar to that observed for human Sco1 and a homolog from Bacillus subtilis. The Cu–ySco1 structure, obtained by soaking apo-ySco1 crystals in copper ions, reveals an unexpected copper-binding site involving Cys181 and Cys216, cysteine residues present in ySco1 but not in other homologs. The conserved CXXXC cysteines, Cys148 and Cys152, can undergo redox chemistry in the crystal. An essential histidine residue, His239, is located on a highly flexible loop, denoted the Sco loop, and can adopt positions proximal to both pairs of cysteines. Interactions between ySco1 and its partner proteins yeast Cox17 and yeast COX2 are likely to occur via complementary electrostatic surfaces. This high-resolution model of a eukaryotic Sco protein provides new insight into Sco copper binding and function.     

Morphological development and cytochrome c oxidase activity in Streptomyces lividans are dependent on the action of a copper bound Sco protein

Copper has an important role in the life cycle of many streptomycetes, stimulating the developmental switch between vegetative mycelium and aerial hyphae concomitant with the production of antibiotics. In streptomycetes, a gene encoding for a putative Sco-like protein has been identified and is part of an operon that contains two other genes predicted to handle cellular copper. We report on the Sco-like protein from Streptomyces lividans (Sco^Sl) and present a series of experiments that firmly establish a role for Sco^Sl as a copper metallochaperone as opposed to a role as a thiol-disulphide reductase that has been assigned to other bacterial Sco proteins. Under low copper concentrations, a Δsco mutant in S. lividans displays two phenotypes; the development switch between vegetative mycelium and aerial hyphae stalls and cytochrome c oxidase (CcO) activity is significantly decreased. At elevated copper levels, the development and CcO activity in the Δsco mutant are restored to wild-type levels and are thus independent of Sco^Sl. A CcO knockout reveals that morphological development is independent of CcO activity leading us to suggest that Sco^Sl has at least two targets in S. lividans. We establish that one Sco^Sl target is the dinuclear Cu_A domain of CcO and it is the cupric form of Sco^Sl that is functionally active. The mechanism of cupric ion capture by Sco^Sl has been investigated, and an important role for a conserved His residue is identified.     

Evaluation of SCO1 deletion on Saccharomyces cerevisiae metabolism through a proteomic approach

The Saccharomyces cerevisiae gene SCO1 has been shown to play an essential role in copper delivery to cytochrome c oxidase. Biochemical studies demonstrated specific transfer of copper from Cox17p to Sco1p, and physical interactions between the Sco1p and Cox2p. Deletion of SCO1 yeast gene results in a respiratory deficient phenotype. This study aims to gain a more detailed insight on the effects of SCO1 deletion on S. cerevisiae metabolism. We compared, using a proteomic approach, the protein pattern of SCO1 null mutant strain and wild-type BY4741 strain grown on fermentable and on nonfermentable carbon sources. The analysis showed that on nonfermentable medium, the SCO1 mutant displayed a protein profile similar to that of actively fermenting yeast cells. Indeed, on 3% glycerol, this mutant displayed an increase of some glycolytic and fermentative enzymes such as glyceraldehyde-3-phosphate dehydrogenase 1, enolase 2, pyruvate decarboxylase 1, and alcohol dehydrogenase 1. These data were supported by immunoblotting and enzyme activity assay. Moreover, the ethanol assay and the oxygen consumption measurement demonstrated a fermentative activity in SCO1 mutant on respiratory medium. Our results suggest that on nonfermentable carbon source, the lack of Sco1p causes a metabolic shift from respiration to fermentation.