MEMORY AND IMPRINTING EFFECTS IN MULTIENZYME COMPLEXES .1. ISOLATION,DISSOCIATION, AND REASSOCIATION OF A PHOSPHORIBULOKINASE-GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASE COMPLEX FROM CHLAMYDOMONAS-REINHARDTII CHLOROPLASTS
L. Avilan et al., MEMORY AND IMPRINTING EFFECTS IN MULTIENZYME COMPLEXES .1. ISOLATION,DISSOCIATION, AND REASSOCIATION OF A PHOSPHORIBULOKINASE-GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASE COMPLEX FROM CHLAMYDOMONAS-REINHARDTII CHLOROPLASTS, European journal of biochemistry, 246(1), 1997, pp. 78-84
A bienzyme complex made up of phosphoribulokinase and glyceraldehyde-3
-phosphate dehydrogenase has been isolated and purified from chloropla
sts of Chlamydomonas reinhardtii. The complex contains four phosphorib
ulokinase and eight glyceraldehyde-3-phosphate dehydrogenase polypepti
de chains. As phosphoribulokinase is dimeric and glyceraldehyde-3-phos
phate dehydrogenase tetrameric, it is concluded that the complex compr
ises two phosphoribulokinase and two glyceraldehyde-3-phosphate dehydr
ogenase molecules. Its overall molecular mass is 460 kDa, which is in
excellent agreement with its stoichiometry. Moreover, owing to the nat
ure of the two enzymes, this complex must catalyse two nonconsecutive
reactions. The bienzyme complex tended to spontaneously dissociate int
o the free enzymes upon dilution. This dissociation process was consid
erably promoted by reducing agents such as dithiothreitol or reduced t
hioredoxin. The kinetics of the dissociation process induced by dithio
threitol or reduced thioredoxin were paralleled by an increase of acti
vity of phosphoribulokinase. The dissociation of the complex was rever
sible. If oxidized phosphoribulokinase and glyceraldehyde-3-phosphate
dehydrogenase were mixed, a certain amount of the complex was formed.
The reconstituted complex displayed properties that were indistinguish
able from those of the native complex extracted from chloroplasts of C
hlamydomonas reinhardtii. These results suggest that the concentration
of the complex in vivo may vary depending on the light intensity.