C. Reinbothe et al., A LIGHT-INDUCED PROTEASE FROM BARLEY PLASTIDS DEGRADES NADPH, PROTOCHLOROPHYLLIDE OXIDOREDUCTASE COMPLEXED WITH CHLOROPHYLLIDE, Molecular and cellular biology, 15(11), 1995, pp. 6206-6212
The NADPH:protochlorophyllide oxidoreductase precursor protein (pPorA)
of barley (Hordeum vulgare L. cv. Carina), synthesized from a full-le
ngth cDNA clone by coupling in vitro transcription and translation, is
a catalytically active protein, It converts protochlorophyllide to ch
lorophyllide in a light- and NADPH-dependent manner. At least the pigm
ent product of catalysis remains tightly bound to the precursor protei
n. The chlorophyllide-pPorA complex differs markedly from the protochl
orophyllide-pPorA complex: with respect to sensitivity to attack by a
light-induced, nucleus-encoded, and energy-dependent protease activity
of barley plastids, The pPorA-chlorophyllide complex is rapidly degra
ded, in contrast to pPorA-protochlorophyllide complexes containing or
lacking NADPH, which are both resistant to protease treatment, Unexpec
tedly, pPorA devoid of its substrates or products mas less sensitive t
o proteolysis than the pPorA-chlorophyllide complex, suggesting that b
oth substrate binding and product formation during catalysis had cause
d differential changes in protein conformation.