Lectin activity of Bacillus thuringiensis parasporal inclusion proteins

Parasporal inclusion proteins from a total of 151 Bacillus thuringiensis strains, consisting of 139 Japanese isolates and the type strains of 12 H serovars, were screened for haemagglutination (HA) activity against sheep erythrocytes. Of 58 B. thuringiensis strains with HA activity, nine strains exhibited high activity and the remaining 49 strains were moderately active. The strains with high HA activity were derived from phylloplanes and soils of five geographically different localities, and belonged to H serovars kurstaki and other undefined serotype(s). The HA activities in the four selected strains were generated only when alkali-solubilised parasporal inclusion proteins were proteolytically processed. Furthermore, the lectin activity of the four strains was strongly inhibited by preincubation with N-acetylgalactosamine. The lectin-producing B. thuringiensis strains were heterogeneous in other biological activities of parasporal inclusions: insecticidal activity and cytocidal action on human leukaemia T cells.     

Tumor inhibitors having potential for interaction with mercapto enzymes and/or coenzymes: A review

On the basis of extensive information on in vivo metabolism as well as biomimetic reactions using simple SH compounds and some enzymes, numerous chemical functions which react with SH groups are divided into two classes; i.e., one which involves electrophilic addition (EA) to an SH group and the other which features displacement reactions (DR) by the SH group (see Tables 1 and 2). The known tumor inhibitors are accordingly classified into EA and DR types. Biomimetic reactions of tumor inhibitors with model compounds of SH enzymes (or coenzymes) and with some SH enzymes themselves are described. Finally, as enhancement factors for the antitumor activity, the roles of hydrogen-bonding, neighboring group participation, and effect of ester side chains are introduced. These discussions may serve in the development of the new SH alkylating antitumor agents.     

Inhibition of interleukin-2 receptor (CD25) expression induced on T cells from children with acute lymphoblastic leukemia

 Peripheral blood lymphocytes obtained from children with acute lymphoblastic leukemia (ALL) at onset were studied for the expression of interleukin-2 (IL-2) receptor α-chain (CD25) by two-color flow-cytometric analysis. Stimulated with anti-CD3 monoclonal antibody (mAb) alone, CD25 expression was significantly suppressed in CD4⁺ T cells from 27 of 48 (56.3%) cases and in CD8⁺ T cells from 29 of 48 (60.4%) cases. When stimulated with anti-CD3 mAb plus phorbol 12-myristate 13-acetate (PMA), CD25 expression was clearly restored in certain cases of ALL. When PMA plus ionomycin were used for stimulation of T cells, CD25 was inducible in a majority of cases. Interestingly CD25 expression upon anti-CD3 mAb stimulation was recovered after complete remission had been achieved. These observations suggest the presence in ALL children at onset of an in vitro defect in the signal transduction pathway of the T-cell-receptor/CD3 complex, resulting in inefficient CD25 expression. However, immune-staining analysis indicated that protein kinase C was normally translocated from the cytosol fraction to the cell membrane fraction. The mobilization of cytoplasmic free calcium is also normal. Received: 27 March 1996 / Accepted: 23 December 1996     

Dependence of removal of sperm-specific proteins from Xenopus sperm nuclei on the phosphorylation state of nucleoplasmin

In Xenopus laevis , nucleoplasmin from fully grown oocytes is not highly phosphorylated, but is more extensively phosphorylated during oocyte maturation to retain this state until mid-blastula transition. Incubation of demembranated sperm with nucleoplasmin from oocytes or mature eggs revealed that egg nucleoplasmin is twice as potent as oocyte nucleoplasmin in removing sperm-specific basic proteins from chromatin (protamine-removing activity: PRA). Dephosphorylation of egg nucleoplasmin by alkaline phosphatase induced a remarkable decline of PRA in nucleoplasmin. Treatment of oocyte nucleoplasmin with cdc2 protein kinase induced an increase of the extent of phosphorylation, but to a level lower than that exhibited by egg nucleoplasmin, suggesting the involvement of other unspecified kinase(s) in phosphorylating nucleoplasmin during oocyte maturation. Incubation of sperm with cdc2 kinase induced selective phosphorylation of sperm-specific basic proteins, accompanied by their enhanced removal from sperm chromatin upon exposure to high-salt solutions. These results suggest that removal of sperm-specific basic proteins from sperm chromatin in fertilized eggs is facilitated by phosphorylation of both nucleoplasmin and sperm-specific basic proteins.