Prediction of partial membrane protein topologies using a consensus approach

We have developed a method to reliably identify partial membrane protein topologies using the consensus of five topology prediction methods. When evaluated on a test set of experimentally characterized proteins, we find that approximately 90% of the partial consensus topologies are correctly predicted in membrane proteins from prokaryotic as well as eukaryotic organisms. Whole-genome analysis reveals that a reliable partial consensus topology can be predicted for approximately 70% of all membrane proteins in a typical bacterial genome and for approximately 55% of all membrane proteins in a typical eukaryotic genome. The average fraction of sequence length covered by a partial consensus topology is 44% for the prokaryotic proteins and 17% for the eukaryotic proteins in our test set, and similar numbers are found when the algorithm is applied to whole genomes. Reliably predicted partial topologies may simplify experimental determinations of membrane protein topology.     

GROWTH-INHIBITORS AND GROWTH-PROMOTERS IN ENTEROMORPHA COMPRESS A (CHLOROPHYTA)1

Methanol extracts from the alga Enteromorpha compressa (L.) Grev. contain substances which inhibit the elongation of Lepidium roots. Chromatographic separation of the inhibiting substances revealed that one of the inhibitory zones of the chromatograms had properties of the so-called inhibitor β. Neither abscisic acid (ABA) nor lunularic acid proved to be responsible for the growth-inhibiting property of this zone. Moreover, the extracts contain substances which promote the elongation of Avena coleoptile segments. One of these substances could be tentatively identified as indole-3-acetic acid by thin-layer and gas-liquid chromatography. (In addition to indole-3-acetic acid a second growth-promoting factor with the properties of the so-called accelerator α could be detected.)     

THE CYST-THECA RELATIONSHIP IN CALCIODINELLUM OPEROSUM EMEND. (PERIDINIALES, DINOPHYCEAE) AND A NEW APPROACH FOR THE STUDY OF CALCAREOUS CYSTS

The paratabulate calcareous cyst of Calciodinellum operosum Deflandre was recorded in a sediment trap sample collected in the Bay of Naples (Tyrrhenian Sea, Italy). The germination of this resting stage produced a phototrophic vegetative cell that had the typical plate pattern of a Scrippsiella species. The cyst morphotypes, observed in a clonal culture of this species, ranged from cysts with well-developed paratabulation to cysts in which the paratabulation was barely visible, to cysts covered by irregularly shaped crystals. The analysis of thin sections of the calcareous cysts using the polarized light microscope equipped with crossed nicols and a gypsum plate showed that the optical orientation of the calcite crystals was tangential in all the morphotypes examined. We suggest that the crystallographic method we describe might provide insights for calcareous cyst taxonomy and phylogeny .