Figure 2.

Thf1 encodes a light-regulated plastid-localized protein. The figure demonstrates import of ³⁵S-radiolabeled protein into isolated chloroplasts and association of Thf1 with both stromal and thylakoid fractions. Labeled proteins were produced via in vitro transcription/translation and products were separated on SDS-polyacrylamide gels. The largest proteins represent the precursor form, whereas the next smaller band represents the mature, processed form of each protein (Thf1, 26.8 kD; LHCP, 27 kD; p36, 36 kD). In addition to labeling Thf1 (A), ³⁵S-labeled LHCP, a protease-accessible thylakoid protein where a degraded form of the protein is found in the thermolysin-treated thylakoid fraction (B), and p36, a protein found in the inner envelope membrane (C), were prepared. For each labeled protein, further fractionation and/or treatment were performed and products were separated; they represent translation product (TP), chloroplasts after import (C), stroma fraction (S), thylakoids (T), and thylakoids treated with thermolysin protease (T+).