CHARACTERIZATION OF CD-INDUCED LOW-MOLECULAR-WEIGHT PROTEIN IN A N-2-FIXING CYANOBACTERIUM ANABAENA-DOLIOLUM WITH SPECIAL REFERENCE TO CO- MULTIPLE TOLERANCE/

This study presents information on the production of a 3.3 kDa protein , rich in cadmium and -SH contents and sensitive to buthionine-sulfoxi mine (BSO), in a diazotrophic cyanobacterium Anabaena doliolum followi ng 20 mu M Cd exposure. The absorbance at A(254) was lost on acidifica tion and could not be resumed even after neutralization. The radioacti ve sulfur (H-2 (SO4)-S-35) labeling depicted maximum incorporation of S-35 in the 3.3 KDa fraction. Synthesis of this protein was blocked by transcriptional and translational inhibitors, and resumed on glutathi one supplementation. This suggests that its synthesis is independent o f genetic regulation. The synthesis of this protein was stimulated by CoCl2 and inhibited 85% by dark incubation and 100% by L-azaserine and DCCD. This demonstrates the participation of energy in its synthesis. Compared to the untreated control the Cd-pregrown A. doliolum however , showed an increased final yield and higher tolerance index (TI) when exposed to metals like copper, nickel, lead, iron and zinc, anaerobio sis, heat, and cold shocks as well as X-rays and UV-B irradiations. Th is study suggests that the low molecular weight cadmium-induced protei n of A. doliolum largely resembles the higher plant phytochelatins (PC s) and offers not only co-tolerance to different heavy metals but also provides multiple tolerance to a host of environmental stresses.