Import and subplastid localization of precursors.
Isolated chromoplasts containing 2.0 μg chlorophyll/mg protein were
incubated with radiolabeled in vitro translation products (lanes tp) in
the presence (+ATP) or absence (−ATP) of ATP, as described in
Methods. Following import, chromoplasts were
recovered without protease posttreatment (lanes C) or with protease
posttreatment (lanes CP). Untreated chromoplasts were subfractionated
into stroma (lanes S) and total membranes (lanes TM). Equivalent
aliquots of membranes were extracted with NaOH (lanes MN) or treated
with protease (lanes MP). One microliter of radiolabeled translation
product and 15 μL of each sample (representing 7.5 μL of the
original radiolabeled translation product added to the import reaction)
were analyzed by SDS-PAGE (A–D, 12.5%; E, 7.5%) and fluorography.
Precursors utilized for import were: Rbcs (A), OE17 (B), OE33 (C), LHCP
(D), and Pftf (E). p, pOE17; i, iOE17; m, mOE17.