Maize non-photosynthetic ferredoxin precursor is mis-sorted to the intermembrane space of chloroplasts in the presence of light

Citation
T. Hirohashi et al., Maize non-photosynthetic ferredoxin precursor is mis-sorted to the intermembrane space of chloroplasts in the presence of light, PLANT PHYSL, 125(4), 2001, pp. 2154-2163
Citations number
60
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Plant Sciences","Animal & Plant Sciences
Journal title
PLANT PHYSIOLOGY
ISSN journal
0032-0889 → ACNP
Volume
125
Issue
4
Year of publication
2001
Pages
2154 - 2163
Database
ISI
SICI code
0032-0889(200104)125:4<2154:MNFPIM>2.0.ZU;2-4
Abstract
Preprotein translocation across the outer and inner envelope membranes of c hloroplasts is an energy-dependent process requiring ATP hydrolysis. Severa l precursor proteins analyzed so far have been found to be imported into is olated chloroplasts equally well in the dark in the presence of ATP as in t he light where ATP is supplied by photophosphorylation in the chloroplasts themselves. We demonstrate here that precursors of two maize (Zea mays I,. cv Golden Cross Bantam) ferredoxin isoproteins, pFdI and pFdIII, show disti nct characteristics of import into maize chloroplasts. pFdI, a photosynthet ic ferredoxin precursor, was efficiently imported into the stroma of isolat ed maize chloroplasts both in the light and in the dark. In contrast pFdIII , a non-photosynthetic ferredoxin precursor, was mostly mis-sorted to the i ntermembrane space of chloroplastic envelopes as an unprocessed precursor f orm in the light but was efficiently imported into the stroma and processed to its mature form in the dark. The mis-sorted pFdIII, which accumulated i n the intermembrane space in the light, could not undergo subsequent import into the stroma in the dark, even in the presence of ATP. However, when th e mis-sorted pFdIII was recovered and used for a separate import reaction, pFdIII was capable of import into the chloroplasts in the dark, pFNRII, a f erredoxin-NADP(+) reductase isoprotein precursor, showed import characteris tics similar to those of pFdIII. Moreover, pFdIII exhibited similar import characteristics with chloroplasts isolated from wheat (Pennisetum americanu m) and pea (Pisum sativum cv Alaska). These findings suggest that the trans location of precursor proteins across the envelope membranes of chloroplast s may involve substrate-dependent light-regulated mechanisms.