Characterization of RuBP Carboxylase/Oxygenase of the N. tabacum Mutant Series “Consolation” with Homologous and Non-Homologous Antisera

T he m o la r ra tio o f R u B P carb o x y lase /o x y g en ase to th e C F , com plex w as d e te rm in ed in the wild type N. tabacum var. JW B an d in v a rio u s N. tabacum m u ta n ts , w hich d iffer w ith respect to th e ir c h lo ro p las t s tru c tu re an d th e ir p h o to sy n th e tic an d p h o to re sp ira to ry activ ity . It a p ­ pears th a t the ra tio R u B P carb o x y lase /o x y g e n ase /C F , is n o t co n s tan t in the d ifferen t m u ta n ts , and a p p a re n tly dep en d s on th e c h lo ro p la s t s tru c tu re an d th e p h o to sy n th e tic capacity . In the green p h en o ty p es o f N. tabacum var. C o n so la tio n , var. N C 95 an d var. X an th i, w hose lam ellar system consists o f a b a lan ced ra tio o f g ra n a a n d in te rg ra n a reg ions the ra tio is 3 4 R u B P c a r­ boxylase/oxygenase m olecu les p e r C F , com plex . In ch lo ro p las ts o f the yellow -green m u ta n t Su /su , a n d the yellow m u ta n t o f N. tabacum var. C o n so la tio n , w hose lam ellar system consists o f ex tended in te rg ran a reg ions an d low stack ed g ra n a the R uB P c arb o x y lase /o x y g en ase /C F , ra tio is reduced to a b o u t o ne half. T he a u rea m u ta n t N. tabacum Su /su var. aurea an d the yel­ low -green lea f p a tch es o f v a rieg a ted tabacum va r. X a n th i a re ch arac te rized by the fact th a t one m olecule R uB P ca rb o x y lase /o x y g en ase co rre la te s to tw o C F , com plexes. A lso in the tw o N. tabacum m u ta n ts S u /su a n d C o n so la tio n green , th a t exh ib it a 30% h igher p h o to re sp ira tio n these m o la r ra tio s d ep en d o n th e c h lo ro p la s t s tru c tu re . T he d e te rm in a tio n o f th e m ax im al b in d in g o f a n tib o d ies o u t o f h o m o lo g o u s an d n o n -h o m o logous a n tise ra o n to R u B P carb o x y lase /o x y g en ase o f th e N. tabacum m u ta n t C o n so la tio n show ed, th a t the enzym e o f the g reen m u ta n t, w h ich exh ib its a h igher oxygenase activ ity , has in c o m p ariso n to the yellow -green an d yellow p h e n o ty p e o f th is m u ta n t series and a lso in co m ­ p a riso n to th e w ild type a 30 p e r cen t h ig h er a n tib o d y b in d in g capacity . T hese d ifferences in a n tib o d y b in d in g a re sh o w n in b o th th e reg ion o f enzym e a n tib o d y equivalence an d th a t o f a n tib o d y excess. W ith th e m eth o d s o f en zy m e-an tib o d y p re c ip ita tio n in ag aro se gels these d if­ ferences o f enzym es, ex h ib itin g h ig h er o r low er oxygenase activ ities, c an n o t be de tected . T he na tive enzym es an d th e large su b u n its o f th e enzym e o f the th ree C o n so la tio n m u ta n ts yield in these test reac tio n s w ith the enzym e o f th e w ild -ty p e fusing p re c ip ita tio n bands. T rea tm e n t w ith th e chem ical ag en t h y d ro x y lam in e , as well as h ea t trea tm e n t a t 50 °C a lte rs the enzym e c o n fo rm a tio n to such an ex ten t th a t th e an tib o d y b in d in g capacity is increased by 70% . T h e d ifference in th e h ig h er a n tib o d y b in d in g cap ac ity o f the enzym e o f the green m u ta n t o f N. tabacum var. C o n so la tio n is m a in ta in ed a lso a f te r these chem ical m od ifications.