Role of Elongation Factor G in the Inhibition of the Synthesis of the D1 Protein of Photosystem II Under Oxidative Stress

Abstract

Oxidative Stress Inhibits The Repair Of Photodamaged Photosystem Ii (Psii) Via Suppression, By Reactive Oxygen Species (Ros), Of The Synthesis De Novo Of Proteins That Are Required For The Repair Of Psii, Such As The D1 Protein, At The Level Of Translational Elongation. Using A Translation System From The Cyanobacterium Synechocystis Sp. Pcc 6803 In Vitro, We Recently Demonstrated That Three Isoforms Of Elongation Factor G (Ef-G) Are The Primary Targets Of Inhibition By Ros Within The Translational Machinery (Kojima Et Al. 2007). In The Present Study, We Examined The Role Of Another Putative Ef-G Encoded By Slr1105 In The Genome Of Synechocystis. When The Reduced Form Of Slr1105 Was Added To The Translation System In Vitro, Which Had Been Inhibited By Exogenous H2O2, The Translation System Resumed Synthesis Of The D1 Protein. Overexpression Of Slr1105 In Another Cyanobacterium Synechococcus Sp. Pcc 7942 Increased The Tolerance Of Cells To H2O2 In Terms Of Protein Synthesis. These Observations Suggest That Oxidation Of Slr1105, As Well As That Of The Other Three Isoforms Of Ef-G, Is Critical For The Inhibition Of Translation By Ros.