Figure 8.

In Vitro Import into Chloroplasts.

Radiolabeled proteins were incubated with intact chloroplasts for 20 min under the import condition at which time the chloroplasts were reisolated and fractions containing imported proteins subjected to SDS-PAGE, followed by fluorography. Black lines separate grouping of images from different portions of the same gel. The “tl” lane shows 10% of the translation product subjected to the assay; “imp” lanes represent the imported protein.

(A) Chloroplasts with imported protein were treated with thermolysin or trypsin as indicated by the + and − symbols. Triton X-100 (Tx-100) was also included in some reactions.

(B) Chloroplasts were hypotonically lysed and fractionated by centrifugation into a supernatant that contains soluble proteins (S1) and a pellet. The pellet was resuspended in Na₂CO₃ and fractionated by centrifugation into a supernatant containing peripheral membrane proteins (S2) and a pellet (P).