A peroxidase homologue and novel plastocyanin located by proteomics to theArabidopsis chloroplast thylakoid lumen

A study by two-dimensional electrophoresis showed that the soluble, lumenal fraction of Arabidopsis thaliana thylakoids can be resolved into 300 prote in spots. After subtraction of low-intensity spots and accounting for low-l evel stromal contamination, the number of more abundant, lumenal proteins w as estimated to be between 30 and 60. Two of these proteins have been ident ified: a novel plastocyanin that also was the predominant component of the total plastocyanin pool, and a putative ascorbate peroxidase. Import studie s shamed that these proteins are routed to the thylakoid lumen by the Sec- and delta pH-dependent translocation pathways, respectively, In addition, n ovel isoforms of PsbO and PsbQ were identified, (C) 2000 Federation of Euro pean Biochemical Societies. Published by Elsevier Science B.V. All rights r eserved.