The chloroplast protein disulfide isomerase RB60 reacts with a regulatory disulfide of the RNA-binding protein RB47

• Published in: Plant and cell physiology 2006-04, Vol.47 (4), p.540-548
• Main Authors: Alergand, T.(Weizmann Inst. of Science, Rehovot (Israel)), Pered-Zehavi, H, Katz, Y, Danon, A
• Format: Article
• Language: English
• Subjects: 2-nitro-5-thiobenzoate; 5′-dithiobis-2-nitrobenzoic acid; Animals; CHLAMYDOMONAS REINHARDTII; Chlamydomonas reinhardtii - enzymology; Chloroplast; CHLOROPLASTE; CHLOROPLASTS; Chloroplasts - enzymology; CLOROPLASTO; Cysteine - analysis; Disulfides - chemistry; Disulfides - metabolism; dithiothreitol; DTNB; DTT; Light; MALDI-TOF; mass spectrometry; matrix-assisted laser desorption ionization time of flight; N-ethylmaleimide; NEM; Oxidation-Reduction; PABP; PABP-interacting protein; Paip; PDI; Phosphorylation; poly(A)-binding protein; Protein disulfide isomerase; Protein Disulfide-Isomerases - chemistry; Protein Disulfide-Isomerases - metabolism; Protein Interaction Mapping; PROTEINAS; PROTEINE; PROTEINS; Redox regulation; Regulatory disulfide; RNA recognition motif; RNA, Messenger - metabolism; RNA, Plant - metabolism; RNA-binding protein; RNA-Binding Proteins - chemistry; RNA-Binding Proteins - metabolism; RRM; TNB; untranslated region; UTR
• ISSN: 0032-0781; 1471-9053
• DOI: 10.1093/pcp/pcj023

Biochemical studies have identified two proteins, RB47 and RB60, that are involved in the light-regulated translation of the psbA mRNA in the chloroplast of the unicellular alga Chlamydomonas reinhardtii. RB47, a member of the eukaryotic poly(A)-binding protein family, binds directly to the 5' untranslated region of the mRNA, whereas RB60, a protein disulfide isomerase (PDI), is thought to bind to RB47 and to modulate its activity via redox and phosphorylation events. Our present studies show that RB47 forms a single disulfide bridge that most probably involves Cysl43 and Cys259. We found that RB60 reacts with high selectivity with the disulfide of RB47, suggesting that the redox states of these two redox partners are coupled. Kinetics analysis indicated that RB47 contains two fast reacting cysteines, of which at least one is sensitive to changes in pH conditions. The results support the notion that light controls the redox regulation of RB47 function via the coupling of RB47 and RB60 redox states, and suggest that light-induced changes in stromal pH might contribute to the regulation.