ALTERED MONOVINYL AND DIVINYL PROTOCHLOROPHYLLIDE POOLS IN BCHJ MUTANTS OF RHODOBACTER-CAPSULATUS - POSSIBLE MONOVINYL SUBSTRATE DISCRIMINATION OF LIGHT-INDEPENDENT PROTOCHLOROPHYLLIDE REDUCTASE
Jy. Suzuki et Ce. Bauer, ALTERED MONOVINYL AND DIVINYL PROTOCHLOROPHYLLIDE POOLS IN BCHJ MUTANTS OF RHODOBACTER-CAPSULATUS - POSSIBLE MONOVINYL SUBSTRATE DISCRIMINATION OF LIGHT-INDEPENDENT PROTOCHLOROPHYLLIDE REDUCTASE, The Journal of biological chemistry, 270(8), 1995, pp. 3732-3740
In land plants in particular, it has been well established that chloro
phyll intermediates, Mg-protoporphyrin, Mg-protoporphyrin monomethyles
ter, protochlorophyllide, and chlorophyllide occur as monovinyl and di
vinyl forms, The pool of monovinyl and divinyl intermediates differ ac
cording to species, age of tissue, and light regime, In this study, we
investigated the monovinyl and divinyl characteristics of protochloro
phyllide and chlorophyllide in the purple non-sulfur photosynthetic eu
bacterium Rhodobacter capsulatus. Our results indicate that mutations
in genes known to completely block the reduction of protochlorophyllid
e to chlorophyllide (such as bchN, bchB, and bchL mutants), accumulate
a pool of monovinyl and divinyl forms of protochlorophyllide just as
observed in plants, However, we also observed that directed insertion
and deletion mutations in bchJ, a gene located in the photosynthesis g
ene cluster, affected the ratio of monovinyl and divinyl protochloroph
yllide, Specifically, bchJ-disrupted strains accumulate reduced levels
of bacteriochlorophyll concomitant with the accumulation of divinyl p
rotochlorophyllide, Mutants of bchJ in combination with a second mutat
ion in bchL still produce a mixed pool of monovinyl and divinyl protoc
hlorophyllide; however, the ratio of monovinyl to divinyl protochlorop
hyllide is skewed in favor of divinyl protochlorophyllide. These resul
ts thus identify bchJ as the first sequenced gene that affects the div
inyl to monovinyl ratio of photopigment intermediates in any photosynt
hetic organism, In addition, the results of our study also suggest tha
t light-independent protochlorophyllide reductase is discriminatory fo
r a monovinyl substrate.