Immunogold localization of acyl carrier protein in plants and Escherichia coli: Evidence for membrane association in plants

Immunogold labelling was used to study the distribution of acyl carrier protein (ACP) in Escherichia coli and a variety of plant tissues. In E. coli, ACP is distributed throughout the cytoplasm, confirming the observation of S. Jackowski et al. (1985, J. Bacteriol., 162, 5–8_. In the mesocarp of Avocado (Persea americana) and maturing seeds of oil-seed rape (Brassica napus cv. Jet Neuf), over 95% of the ACP is localised to plastids. The protein is almost exclusively located in the chloroplasts of leaf material from oil-seed rape. Approximately 80% of the gold particles associated with the ACP were further localized to the thylakoid membrane of the chloroplast. Since acetyl-CoA carboxylase has been reported to be localized to the thylakoid membrane (C.G. Kannangara and C.J. Jensen, 1975, Eur. J. Biochem., 54, 25–30), these results are consistent with the view that the two sequential enzymes in fatty-acid synthesis are in close spacial proximity.Abbreviations ACC acetyl CoA carboxylase - ACP acyl carrier protein - FAS fatty-acid synthetase