Distribution of thioredoxins f and m with respect to seven light-activated enzymes and three redox-insensitive proteins in pea leaf chloroplasts

Immunocytolocalization experiments indicate that thioredoxin m is non-randomly distributed with respect to fructose bisphosphatase (EC 3.1.3.11), sedoheptulose bisphosphatase (EC 3.1.3.37), phosphoribulokinase (EC 2.7.1.19), NADP-linked glyceraldehyde-3-P dehydrogenase (EC 1.2.1.13), P-glycerate kinase (EC 2.7.2.3), aldolase (EC 4.1.2.13), ADP-glucose pyrophosphorylase (EC 2.7.7.27), NADP-dependent malate dehydrogenase (EC 1.1.1.82), ATP synthase (CF1, EC 3.6.1.34) and heat shock protein 70 (Hsp70) in pea leaf chloroplasts. Thioredoxin f is distributed non-randomly with respect to each of these enzymes and proteins except sedoheptulose bisphosphatase and the B subunit of glyceraldehyde-3-P dehydrogenase. These data, in combination with the results of binding experiments and activation assays reported by other laboratories, suggest that both thioredoxins may be involved in regulation of the activity of the light-activated Calvin cycle enzymes. Co-localization with enzymes not known to be light modulated is consistent with the notion that the thioredoxins might have some secondary function in the chloroplast, such as acting as linker proteins.