The polypeptide heterogeneity of the chloroplast envelope has been compared with these of other fractions of Spinach chloroplasts: thylakoïds and stroma by means of SDS-polyacrylamide gel electrophoresis. The envelope electrophoretic pattern shows many polypeptides whose mobility differ from those of the thylakoïds. The possible identity of the small subunit of RudPcarboxylase with a polypeptide of the chloroplast external membrane is discussed.
