Characterization of Cd-induced low molecular weight protein in a N-fixing cyanobacterium Anabaena doliolum with special reference to co-/multiple tolerance

Abstract

This study presents information on the production of a 3.3 kDaprotein, rich in cadmium and -SH contents and sensitive tobuthionine-sulfoximine (BSO), in a diazotrophic cyanobacterium Anabaenadoliolum following 20 μM Cd exposure. The absorbance at A was lost on acidification and could not be resumedeven after neutralization. The radioactive sulfur(HSO)labeling depicted maximum incorporation of Sin the 3.3 KDa fraction. Synthesis of this protein was blocked bytranscriptional and translational inhibitors, and resumed on glutathionesupplementation. This suggests that its synthesis is independent ofgenetic 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. Comparedto the untreated control the Cd-pregrown A. doliolum however, showed anincreased final yield and higher tolerance index (TI) when exposed tometals like copper, nickel, lead, iron and zinc, anaerobiosis, heat,and cold shocks as well as X-rays and UV-B irradiations. This studysuggests that the low molecular weight cadmium-induced protein ofA. doliolum largely resembles the higher plant phytochelatins (PCs)and offers not only co-tolerance to different heavy metals but alsoprovides multiple tolerance to a host of environmental stresses.© Rapid Science 1998.