Open AccessSenescence-Induced, Thylakoid-Bound Diisopropylfluorophosphate-Binding Protein in Spinach
Author(s) -
Shinji Kawasaki,
Junko Takeuchi
Publication year - 1989
Publication title -
plant physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.554
H-Index - 312
eISSN - 1532-2548
pISSN - 0032-0889
DOI - 10.1104/pp.90.1.338
Subject(s) - spinacia , thylakoid , biochemistry , spinach , kilodalton , photosystem ii , binding protein , biology , pmsf , differential centrifugation , photosystem , gel electrophoresis , chemistry , chloroplast , enzyme , photosynthesis , gene
Changes in diisopropylfluorophosphate (DFP)-binding proteins during development and senescence of spinach (Spinacia oleracea) leaves were followed using [(3)H]DFP and sodium dodecylsulfate-polyacrylamide gel electrophoresis-fluorography. Experiments using a series of aging stages of leaves attached to plants and ones with detached leaves stored in the dark both showed that a protein of 38 kilodaltons was the only major DFP-binding protein in the membrane fraction and that its DFP-binding increased markedly as senescence proceeded, corresponding with the degradation of leaf protein. DFP binding to the 38-kilodalton protein was not affected by membrane solubilization with Triton X-100, and gradually decreased upon preservation of the membranes. The DFP binding was inhibited completely by phenylmethane-sulfonyl fluoride and slightly by p-chloromercuribenzoic acid, suggesting a serine protease-like character of the protein and a possible contribution of SH residues to the binding. Both differential and Percoll-gradient centrifugation indicated that the 38-kilodalton protein was localized in thylakoid membranes. The sedimentation behavior of the detergent-solubilized protein indicated that it belongs to a complex different from photosystem I, photosystem II, or coupling factor 1 of the ATP-synthesizing complex.