Distinct and overlapping binding sites for IKP104 and vinblastine on tubulin

IKP104 is one of a group of tubulin-binding drugs whose interaction with tubulin suggests that it may bind to the protein at or close to the region where vinblastine binds. By itself IKP104 is a potent enhancer of tubulin decay as evidenced by the fact that it induces the exposure of the sulfhydryl groups and hydrophobic areas on tubulin. In this respect, IKP104 differs from vinblastine and other drugs such as phomopsin A, dolastatin 10, rhizoxin, and maytansine which are competitive or noncompetitive inhibitors of vinblastine binding. In contrast, however, in the presence of colchicine, IKP104 behaves differently and strongly stabilizes tubulin, to an extent much greater than does colchicine alone. IKP104 appears to have two classes of binding site on tubulin, differing in affinity; the acceleration of decay appears to be mediated by the low-affinity site (Chaudhuriet al., 1998,J. Protein Chem., in press). We investigated the relationship of the binding of IKP104 and vinblastine. We found that the high-affinity site or sites of IKP104 overlap with or interact with the vinblastine-binding sites, but that the low-affinity site is distinctly different.     

Community dynamics of evergreen broadleaf forests in southwestern Japan. II. Species composition and density of seeds buried in the soil of a climax evergreen oak forest

The species composition and density of seeds in the soil of a climax evergeen oak forest in the Kasugayama Forest Reserve, Nara, Japan were studied by directly extracting seeds from soil samples and using soil samples in planting boxes as the basis of germination tests. A total of 33 species were identified from all seeds collected in 6 stands: 11 evergreen broadleaf, 15 deciduous broadleaf, 2 coniferous, 2 liana, 1 herb, and 2 grass species. Species producing sap fruits and dry fruits accounted for 60% and 40% of the total number of species, respectively. The species composition of all the seeds was independent of the species composition of the forest vegetation. The mean density of the seeds was 22,134 seeds/m²·5 cm.Eurya japonica, of which seeds were found in all soil samples, was the most abundant species, followed byCryptomeria japonica, Ilex micrococca, andBoehmeria longispica. Pioneer species such asMallotus japonicus, Zanthoxylum ailanthoides, andAralia elata were found in all soil samples in spite of the paucity of adult trees in the forest. Seeds of evergreen oaks were relatively aboundant but no viable seeds were found. ViableE. japonica, I. micrococca, Symplocos prunifolia, andB. longispica seeds were abundant.     

A new species,Propherallodus longipterus,from the Philippines and redescription of P. briggsi Shiogaki and Dotsu 1983 (Gobiesocidae: Diplocrepinae)

Ichthyological Research - Propherallodus longipterus sp. nov. (Gobiesocidae: Diplocrepinae) is described on the basis of three specimens (17.0–22.8 mm in standard length: SL) from the...