Chaperonin-Repairable Subtle Incompleteness of Protein Assembly Induced by a Substitution of Hydrogen with Deuterium: Effect of GroE on Deuterated Ribulose 1,5-Bisphosphate Carboxylase

For investigating the effect of slight modification of proteinson their higher-ordered structure, and that of chaperonin onthe functional assembly of proteins, we prepared partially deuteratedribulose 1,5-bisphosphate carboxylase (Rubisco) by cultivatingChlorella ellipsoidea in 100 mol% D₂O medium. Chlorella cellsgrown in the D₂O medium (D-Chlorella) contained almost the sameamount of Rubisco (D-Rubisco) as the cells grown in H₂O medium(H-Chlorella) determined by Western blotting using Rubisco-specificantibody, whereas the activity of D-Rubisco determined by carbonfixation was only 28% of that of Rubisco from H-Chlorella (H-Rubisco).D-Rubisco, however, showed similar K_m and pH and temperatureoptima to those of H-Rubisco as well as similar antibody bindingcapability. The enzyme activity of D-Rubisco was recovered to84% of that of H-Rubisco by the addition of GroE proteins (GroEL,chaperonin 60, and GroES, chaperonin 10), members of the chaperoninfamily produced by Escherichia coli. These data suggest thatD-Rubisco has subtle incompleteness in terms of functional assembly,a situation that is correctable by chaperonin. (Received August 8, 1994; Accepted January 9, 1995)