A simple hypergraph min cut algorithm

We present an algorithm for finding the minimum cut of an edge-weighted hypergraph. It is simple in every respect. It has a short and compact description, is easy to implement and has a surprisingly simple proof of correctness. The runtime is O(jV j 2 log jV j+jV j \Delta jjEjj) where jjEjj is the sum of the cardinalities of the hyperedges

Der Lichtsammelkomplex LHCI-730 des Photosystems I höherer Pflanzen

Der Lichtsammelkomplex LHCI-730 des PSI höherer Pflanzen wird in vivo durch die beiden Chlorophyll a/b-bindenden (LHC-) Proteine Lhca1 und Lhca4 gebildet. Im Rahmen der vorliegenden Arbeit sind Untersuchungen zur funktionellen Assemblierung dieser Proteine durch die in vitro Rekonstitution von rekombinanten Proteinen der Gerste (Hordeum vulgare L.) und Tomate (Lycopersicon esculentum) mit Pigmentextrakten durchgeführt worden. Hierzu wurden die kodierenden Nukleotidsequenzen für die Proteine der Gerste einschließlich ihrer Transitpeptide amplifiziert und unter AF218305 (Lhca1) bzw. AF287276 (Lhca4) in GenBank veröffentlicht. Durch eine vergleichende Analyse von 142 verfügbaren Aminosäuresequenzen für LHC-Proteine angiospermer Pflanzen konnten Protein-Paare mit ungewöhnlicher Übereinstimmung der Transitpeptide identifiziert sowie ein konserviertes Motiv für die LHC-Transitpepide angiospermer Pflanzen abgeleitet werden. Die kodierenden Sequenzen für Lhca1 und Lhca4 wurden in bakterielle Expressionsvektoren (pDS12-RBSII) ligiert und in E. coli (JM101) kloniert. Durch Expression und Aufreinigung bakterieller Proteinextrakte wurde rekombinantes rLhca1 gewonnen. Nach Rekonstitution des aufgereinigten rLhca1-Proteins mit Pigmentextrakten aus Gerste und Tomate konnten stabile rLhca1-Monomere in der ND-Page sowie im Saccharose-Dichtegradienten aufgetrennt werden. Mit der Isolierung stabiler LHCI-730-Dimere in der ND-Page sowie im Saccharose-Dichtegradienten konnte erstmals eine ´heterologe´ Rekonstitution eines LHCI-730 mit rekombinanten Proteinen aus einer mono- (rLhca1 aus Gerste) und einer dikotylen Spezies (rLhca4 aus Tomate) experimentell gezeigt werden

The light-harvesting complex LHCI-730 of higher plant photosystem I

Der Lichtsammelkomplex LHCI-730 des PSI höherer Pflanzen wird in vivo durch die beiden Chlorophyll a/b-bindenden (LHC-) Proteine Lhca1 und Lhca4 gebildet. Im Rahmen der vorliegenden Arbeit sind Untersuchungen zur funktionellen Assemblierung dieser Proteine durch die in vitro Rekonstitution von rekombinanten Proteinen der Gerste (Hordeum vulgare L.) und Tomate (Lycopersicon esculentum) mit Pigmentextrakten durchgeführt worden. Hierzu wurden die kodierenden Nukleotidsequenzen für die Proteine der Gerste einschließlich ihrer Transitpeptide amplifiziert und unter AF218305 (Lhca1) bzw. AF287276 (Lhca4) in GenBank veröffentlicht. Durch eine vergleichende Analyse von 142 verfügbaren Aminosäuresequenzen für LHC-Proteine angiospermer Pflanzen konnten Protein-Paare mit ungewöhnlicher Übereinstimmung der Transitpeptide identifiziert sowie ein konserviertes Motiv für die LHC-Transitpepide angiospermer Pflanzen abgeleitet werden. Die kodierenden Sequenzen für Lhca1 und Lhca4 wurden in bakterielle Expressionsvektoren (pDS12-RBSII) ligiert und in E. coli (JM101) kloniert. Durch Expression und Aufreinigung bakterieller Proteinextrakte wurde rekombinantes rLhca1 gewonnen. Nach Rekonstitution des aufgereinigten rLhca1-Proteins mit Pigmentextrakten aus Gerste und Tomate konnten stabile rLhca1-Monomere in der ND-Page sowie im Saccharose-Dichtegradienten aufgetrennt werden. Mit der Isolierung stabiler LHCI-730-Dimere in der ND-Page sowie im Saccharose-Dichtegradienten konnte erstmals eine ´heterologe´ Rekonstitution eines LHCI-730 mit rekombinanten Proteinen aus einer mono- (rLhca1 aus Gerste) und einer dikotylen Spezies (rLhca4 aus Tomate) experimentell gezeigt werden

Abundantly and Rarely Expressed Lhc Protein Genes Exhibit Distinct Regulation Patterns in Plants

We have analyzed gene regulation of the Lhc supergene family in poplar (Populus spp.) and Arabidopsis (Arabidopsis thaliana) using digital expression profiling. Multivariate analysis of the tissue-specific, environmental, and developmental Lhc expression patterns in Arabidopsis and poplar was employed to characterize four rarely expressed Lhc genes, Lhca5, Lhca6, Lhcb7, and Lhcb4.3. Those genes have high expression levels under different conditions and in different tissues than the abundantly expressed Lhca1 to 4 and Lhcb1 to 6 genes that code for the 10 major types of higher plant light-harvesting proteins. However, in some of the datasets analyzed, the Lhcb4 and Lhcb6 genes as well as an Arabidopsis gene not present in poplar (Lhcb2.3) exhibited minor differences to the main cooperative Lhc gene expression pattern. The pattern of the rarely expressed Lhc genes was always found to be more similar to that of PsbS and the various light-harvesting-like genes, which might indicate distinct physiological functions for the rarely and abundantly expressed Lhc proteins. The previously undetected Lhcb7 gene encodes a novel plant Lhcb-type protein that possibly contains an additional, fourth, transmembrane N-terminal helix with a highly conserved motif. As the Lhcb4.3 gene seems to be present only in Eurosid species and as its regulation pattern varies significantly from that of Lhcb4.1 and Lhcb4.2, we conclude it to encode a distinct Lhc protein type, Lhcb8

Structure of the higher plant light harvesting complex I:in vivo characterization and structural interdependence of the Lhca proteins

We have investigated the structure of the higher plant light harvesting complex of photosystem I (LHCI) by analyzing PSI-LHCI particles isolated from a set of Arabidopsis plant lines, each lacking a specific Lhca (Lhca1-4) polypeptide. Functional antenna size measurements support the recent finding that there are four Lhca proteins per PSI in the crystal structure [Ben-Shem, A., Frolow, F., and Nelson, N. (2003) Nature 426, 630-635]. According to HPLC analyses the number of pigment molecules bound within the LHCI is higher than expected from reconstitution studies or analyses of isolated native LHCI. Comparison of the spectra of the particles from the different lines reveals chlorophyll absorption bands peaking at 696, 688, 665, and 655 nm that are not present in isolated PSI or LHCI. These bands presumably originate from "gap" or "linker" pigments that are cooperatively coordinated by the Lhca and/or PSI proteins, which we have tentatively localized in the PSI-LHCI complex. © 2005 American Chemical Society

Plasticity in the composition of the light harvesting antenna of higher plants preserves structural integrity and biological function

Arabidopsis plants in which the major trimeric light harvesting complex (LHCIIb) is eliminated by antisense expression still exhibit the typical macrostructure of photosystem II in the granal membranes. Here the detailed analysis of the composition and the functional state of the light harvesting antennae of both photosystem I and II of these plants is presented. Two new populations of trimers were found, both functional in energy transfer to the PSII reaction center, a homotrimer of CP26 and a heterotrimer of CP26 and Lhcb3. These trimers possess characteristic features thought to be specific for the native LHCIIb trimers they are replacing: the long wavelength form of lutein and at least one extra chlorophyll b, but they were less stable. A new population of loosely bound LHCI was also found, contributing to an increased antenna size for photosystem I, which may in part compensate for the loss of the phosphorylated LHCIIb that can associate with this photosystem. Thus, the loss of LHCIIb has triggered concerted compensatory responses in the composition of antennae of both photosystems. These responses clearly show the importance of LHCIIb in the structure and assembly of the photosynthetic membrane and illustrate the extreme plasticity at the level of the composition of the light harvesting system

Excitation energy trapping in photosystem I complexes depleted in Lhca1 and Lhca4

AbstractWe report a time-resolved fluorescence spectroscopy characterization of photosystem I (PSI) particles prepared from Arabidopsis lines with knock-out mutations against the peripheral antenna proteins of Lhca1 or Lhca4. The first mutant retains Lhca2 and Lhca3 while the second retains one other light-harvesting protein of photosystem I (Lhca) protein, probably Lhca5. The results indicate that Lhca2/3 and Lhca1/4 each provides about equally effective energy transfer routes to the PSI core complex, and that Lhca5 provides a less effective energy transfer route. We suggest that the specific location of each Lhca protein within the PSI–LHCI supercomplex is more important than the presence of so-called red chlorophylls in the Lhca proteins

Composition and structure of photosystem I in the moss Physcomitrella patens

<p>Recently, bryophytes, which diverged from the ancestor of seed plants more than 400 million years ago, came into focus in photosynthesis research as they can provide valuable insights into the evolution of photosynthetic complexes during the adaptation to terrestrial life. This study isolated intact photosystem I (PSI) with its associated light-harvesting complex (LHCI) from the moss Physcomitrella patens and characterized its structure, polypeptide composition, and light-harvesting function using electron microscopy, mass spectrometry, biochemical, and physiological methods. It became evident that Physcomitrella possesses a strikingly high number of isoforms for the different PSI core subunits as well as LHCI proteins. It was demonstrated that all these different subunit isoforms are expressed at the protein level and are incorporated into functional PSILHCI complexes. Furthermore, in contrast to previous reports, it was demonstrated that Physcomitrella assembles a light-harvesting complex consisting of four light-harvesting proteins forming a higher-plant-like PSI superstructure.</p>