Effect of Chloramphenicol on Formation of Chloroplast Structure and Protein During Greening of Etiolated Leaves of Phaseolus vulgaris.

Greening of leaves of Phaseolus vulgaris in the presence of chloramphenicol inhibits formation of A) total chloroplast protein, B) an easily extractable fraction removed during isolation of chloroplasts in isotonic media by differential centrifugation, and C) the insoluble lamellar fraction which remains after extracting osmotically shocked freeze-dried plastids. The inhibition of insoluble chloroplast protein formation is correlated with decreased formation of lamellae and increased formation of vesicular structures. In contrast, chloramphenicol increases the formation of a fraction not removed during differential centrifugation, but removed by water extraction after osmotic shock and freeze-drying of chloroplasts. Analysis of this fraction by electrophoresis and column chromatography, indicates that the increased accumulation of this protein fraction is largely due to accumulation of a protein which is normally present in this fraction in small quantities. It was suggested that this protein may be a precursor which is normally incorporated into the lamellae. The protein extracted from freeze-dried chloroplasts of chloramphenicol treated chloroplasts contains a smaller proportion of one or more proteins than a similar extract of untreated plastids. However, per plastid, no such difference exists.