Specific characters of small fruiting bodies of the cellular slime mold have been investigated. Cell number increase was most frequently observed during morphogenesis, when number of initial cells exceeds 300. Cell division during morphogenesis was not necessarily requisite for cell differentiation, since cells formed fruiting bodies, even if there was no increase in cell numbers.Ratio of stalk cells to total cells was 14-23% when the total cell number was around 100. The ratio decreased down to 3-7% with cell number increase of a fruiting body.
The partial structure of a spore germination inhibitor from a cellular slime mold, Dictyostelium descoideum was investigated. The molecular weight of this substance is 412 daltons. It contains at least N-(3-methyl-2-butenyl)adenine and an unknown α-amino acid residue. At the concentration of ~0.03 μg/ml (~10−8m), this compound completely inhibited the spore germination of this organism.
Organ-specific variations in blood group H-like activity were observed in developing radish plants. A temporary increase in serological activity was found to occur in the roots at the earlier stages of development. Arabinogalactan-proteins (AGPs) were isolated from primary and mature roots, and investigated for changes in their physicochemical properties, structure, and serological activities. These root AGPs were composed mainly of l-arabinose and d-galactose but were distinguishable from each other in their contents of l-fucose as well as of protein and hydroxyproline. The structures of the carbohydrate moieties of the root AGPs were essentially similar to those of AGPs isolated from seeds and mature leaves in that they consisted of consecutive (1-->3)-linked beta-d-galactosyl backbone chains having side chains of (1-->6)-linked beta-d-galactosyl residues, to which alpha-l-arabinofuranosyl residues were attached in the outer regions. One prominent feature of the primary root AGPs was that they contained appreciable amounts of l-fucose, which was presumably responsible for expression of the serological activity. In their immunological reactions with rabbit anti-radish leaf AGP antibody, the root AGPs were shown to share common antigenic determinant(s) with those of seed and leaf AGPs.
A l-fucose-containing arabinogalactan-protein that strongly inhibited hemagglutination by eel anti-H agglutinin of human O erythrocytes was purified from hot phosphate-buffered saline extracts of mature leaves of rape, Brassica campestris. The purified glycoconjugate consisted of 90% of the polysaccharide moiety comprising l-fucose, l-arabinose, d-galactose, 4-O-methyl-d-glucuronic acid, and d-glucuronic acid, and 4% of the hydroxyproline-rich protein portion. Upon methylation, periodate oxidation, and enzymatic degradation, we found that consecutive β-(→3)-linked d-galactopyranosyl residues constituted a backbone chain of the polysaccharide moiety, to which the side chains of β-(→6)-linked d-galactopyranosyl residues were attached through O-6. Most of l-arabinofuranosyl residues were linked as single units through 0-3 to the side chains while a small quantity of the sugar was present as (1→2)-, (1→3)-, or (1→5)-linked inter-chain residues. Single residues of α-l-fucopyranose, apparently attached to (1→2)-linked l-arabinofuranosyl residues, reacted with eel anti-H precipitin and Aleuria aurantia l-fucose-specific lectin, and were assumed to be crucial in the expression of the H-like activity. The uronosyl residues were also located at the non-reducing terminal ends. Reductive alkaline degradation of the arabinogalactan-protein provided indications that the polysaccharide chains were mainly conjugated through serine-O-glycosidic linkages to the polypeptide core. In an immunoprecipitation test, the rape leaf arabinogalactan-protein cross-reacted with antisera raised against radish leaf arabinogalactan-protein, indicating that these cruciferous arabinogalactan-proteins share common immunodeterminant(s) in their molecules.
Crystal structures of a peptidyl-Lys metalloendopeptidase (MEP) from the edible mushroom Grifola frondosa (GfMEP) were solved in four crystal forms. This represents the first structure of the new family `aspzincins' with a novel active-site architecture. The active site is composed of two helices and a loop region and includes the HExxH and GTxDxxYG motifs conserved among aspzincins. His117, His121 and Asp130 coordinate to the catalytic zinc ligands. An electrostatically negative region composed of Asp154 and Glu157 attracts a positively charged Lys side chain of a substrate in a specific manner. A Tyr133 side chain located on the S1′ pocket had different configurations in two crystal forms and was not observed in the other crystal forms. The flexible Tyr133 plays two roles in the enzymatic function of GfMEP. The first is to provide a hydrophobic environment with Phe83 in order to accommodate the alkyl part of the Lys side chain of a substrate and the second is as a `proton donor' to the oxyanion of the tetrahedral transition state to stabilize the reaction transition state.
