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U Kück

Publications and source records attributed to U Kück.

64 records · Page 4Linked to original sources
PubMed1989

Multipartite structure of mitochondrial DNA in a fungal longlife mutant.

Rearrangements in the mitochondrial genome of the longlife mutant ex1 of the ascomycete Podospora anserina have led to a heterogeneous population of subgenomic molecules. The restriction maps of individual subcircles were established using overlapping recombinant lambda phages isolated from an ex 1 mtDNA/EMBL3 library. The formation of the subcircles and the resulting multipartite organization of the ex1 mtDNA are discussed.

Ascomycota↗
PubMed1988

Mutant phenotypes support a trans-splicing mechanism for the expression of the tripartite psaA gene in the C. reinhardtii chloroplast.

The chloroplast psaA gene of the green unicellular alga Chlamydomonas reinhardtii consists of three exons that are transcribed from different strands. Analysis of numerous nuclear and chloroplast mutants that are deficient in photosystem I activity reveals that roughly one-quarter of them are specifically affected in psaA mRNA maturation. These mutants can be grouped into three phenotypic classes, based on their inability to perform either one or both splicing reactions. The data indicate that the three exons are transcribed independently as precursors which are normally assembled in trans and that the splicing reactions can occur in either order. While some chloroplast mutations could act in cis, the nuclear mutations that fall into several complementation groups probably affect factors specifically required for assembling psaA mRNA.

Base Sequence↗
PubMed1987

Structural and transcription analysis of two homologous genes for the P700 chlorophyll a-apoproteins in Chlamydomonas reinhardii: evidence for in vivo trans-splicing.

The two homologous genes for the P700 chlorophyll a-apoproteins (ps1A1 and ps1A2) are encoded by the plastom in the green alga Chlamydomonas reinhardii. The structure and organization of the two genes were determined by comparison with the homologous genes from maize using data from heterologous hybridizations as well as from DNA and RNA sequencing. While the ps1A2 (736 codons) gene shows a continuous gene organization, the ps1A1 (754 codons) gene possesses some unusual features. The discontinuous gene is split into three separate exons which are scattered around the circular chloroplast genome. Exon 1 (86 bp) is separated by approximately 50 kb from exon 2 (198 bp), which is located approximately 90 kb apart from exon 3 (1984 bp). All exons are flanked by intronic sequences of group II. Transcription analysis reveals that the ps1A2 gene hybridizes with a 2.8-kb transcript, while all exon regions of the ps1A1 gene are homologous to a mature mRNA of 2.7 kb. From our data we conclude that the three distantly separated exonic sequences of the ps1A1 gene constitute a functional gene which probably operates by a trans-splicing mechanism.

Journal Article↗
PubMed1986

Potassium microclimate at the mucosal surface of the proximal and the distal colon of guinea pig.

K+ concentrations were measured with K+ sensitive liquid ion exchanger microelectrodes in situ and in vitro in the mucus layer at the luminal cell surface of the proximal and the distal colon in guinea pig. In a first series of experiments K+ concentrations were increased in the luminal solution from 0 to 70 mmol X l-1; the serosal K+ concentrations were kept in vitro at 5.4 mmol X l-1. In the proximal colon mean K+ concentration in the microclimate was in vitro 7.9 +/- 3.5 mmol X l-1, and independent from mucosal concentrations. In the distal colon in vitro, and in situ in the proximal as well as in the distal colon, K+ concentrations in the microclimate were increased slightly when K+ concentrations were elevated in the luminal solution up to 70 mmol X l-1. In a second series of in vitro studies K+ concentrations were also altered in the serosal fluid. In the proximal and in the distal colon K+ concentrations increased linearly with elevated K+ concentrations in the serosal solutions. A temporarily interrupted mucosal blood flow resulted in a significant increase in the K+ concentration in the microclimate. A paracellular shunt pathway and a high preepithelial diffusion barrier for K+ would explain the observed K+ concentrations in the microclimate at the luminal cell surface.

Animals↗
PubMed1985

Two partially homologous adjacent light-inducible maize chloroplast genes encoding polypeptides of the P700 chlorophyll a-protein complex of photosystem I.

The maize chloroplast chromosome contains two light-inducible genes, ps1A1 and ps1A2, that code for 45% homologous polypeptides of 83.2 and 82.5 kDa designated A1 and A2, respectively. Two types of immunochemical evidence show that the upstream gene, ps1A1, codes for a P700 chlorophyll a-protein at the reaction center of photosystem I of the photosynthetic apparatus. Antibodies against a synthetic peptide with a sequence deduced from the DNA sequence of an unconserved segment of A1 react with polypeptides of P700 chlorophyll-protein (CPI) complexes of maize and pea photosystem I; antibodies prepared against barley CPI immunoprecipitate products of in vitro transcription and translation directed by cloned chloroplast DNA containing this gene. The extensive homology between maize polypeptides A1 and A2 suggests that both may be components of CPI, although CPI has been generally considered to be comprised of two molecules of a single protein of only 66 to 70 kDa. The hexapeptide Asp-Pro-Thr-Thr-Arg-Arg in A2 is also present in another chlorophyll protein, the P680 chlorophyll a-protein of photosystem II, and is partially duplicated in A1. The number and locations of histidyl residues, which have been suggested to serve in chlorophyll binding, are highly conserved between A1 and A2.

Amino Acid Sequence↗
PubMed1985

The onset of senescence is affected by DNA rearrangements of a discontinuous mitochondrial gene in Podospora anserina.

Mapping and transcription studies have revealed that in Podospora anserina the causative agent of senescence, a mitochondrial plasmid (plDNA), is identical with intron 1 of the discontinuous gene for cytochrome-c-oxidase subunit 1 (COI), which is 2 kpb from the discontinuous gene for cytochrome b (Cytb). A mitochondrial mutant (ex1) devoid of the COI, but not of the Cytb gene provides longevity. A molecular model for the onset of senescence is presented.

Amino Acid Sequence↗
PubMed1982

Replication and expression of a bacterial--mitochondrial hybrid plasmid in the fungus Podospora anserina.

Hybrid plasmids consisting of the bacterial plasmid pBR322 and plasmid-like DNA (pl DNA) sequences from the fungus Podospora anserina are not only able to replicate in Escherichia coli but also in the fungus. This was proved by both biophysical and biological evidence involving buoyant density profiles, DNA.DNA hybridization, and restriction analysis--all confirming that pl DNA behaves as a true plasmid. During its amplification in P. anserina, the hybrid plasmid does not lose its prokaryotic coding capacity as shown after retransfer and subsequent cloning in E. coli. P. anserina is able to express both the eukaryotic and the prokaryotic genetic information of the hybrid plasmid because the occurrence of senescence and the production of beta-lactamase could be shown in experiments involving specific hybrid plasmids. In the same systems, it was possible to demonstrate that a hybrid plasmid containing, instead of pl DNA, a pl DNA homologous region of native mtDNA also could function as a true plasmid. This hybrid plasmid contained about 25% of the genetic information pl DNA, which corresponds to about 6% of the genetic information of mtDNA. Thus, the data show that hybrid plasmids may be used to shuttle genetic information between P. anserina and E. coli. hence, through the use of a mtDNA replicon, as evidenced by the pl DNA of P. anserina, another pathway in genetic engineering is established.

DNA Replication↗
PubMed1980

Characterization and cloning of plasmid like DNA of the ascomycete Podospora anserina.

The previously reported existence of plasmid-like (pl) DNA in senescent mycelia of Podospora anserina was confirmed using new methodology. Detailed anaysis of bulk DNA has further shown a possible relationship between pl DNA and mt DNA. According to biophysical and electron microscopic experiments the pl DNA was found to consist of oligomeres having a basic unit with a contour length of 0.75 micrometer corresponding to 2.4 kb. To overcome the handicap that pl DNA is only produced in rather small amounts in the aging mycelia, this DNA was cloned in E. coli after insertion into a bacterial plasmid vector, pBR 322. It was possible to isolate a stable hybrid plasmid consisting of the vector and only one integrated monomere of pl DNA. The composition of this hybrid plasmid was confirmed by restriction endonuclease analysis and heteroduplex formation. A restriction map of the pl DNA is presented and its insertion site onto pBR 322 indicated.

Ascomycota↗