Abstract
The light exposure history and/or binding of different herbicides at the Q(B) site may induce heterogeneity of photosystem II acceptor side conformation that affects D1 protein degradation under photoinhibitory conditions. GTP was recently found to stimulate the D1 protein degradation of photoinactivated photosystem II (Spetea C., Hundal, T., Lohmann, F., and Andersson, B. (1999) Proc. Natl. Acad. Sci. U. S. A. 96, 6547-6552). Here we report that GTP enhances the cleavage of the D1 protein D-E loop following exposure of thylakoid membranes to either high light, low light, or repetitive single turnover flashes but not to trypsin. GTP does not stimulate D1 protein degradation in the presence of herbicides known to affect the accessibility of the cleavage site to proteolysis. However, GTP stimulates degradation that can be induced even in darkness in some photosystem II conformers following binding of the PNO8 herbicide (Nakajima, Y., Yoshida, S., Inoue, Y., Yoneyama, K., and Ono, T. (1995) Biochim. Biophys. Acta 1230, 38-44). Both the PNO8- and the light-induced primary cleavage of the D1 protein occur in the grana membrane domains. The subsequent migration of photo-system II containing the D1 protein fragments to the stroma domains for secondary proteolysis is light-activated. We conclude that the GTP effect is not confined to a specific photoinactivation pathway nor to the conformational state of the photosystem II acceptor side. Consequently, GTP does not interact with the site of D1 protein cleavage but rather enhances the activity of the endogenous proteolytic system.
| Original language | American English |
|---|---|
| Pages (from-to) | 7205-7211 |
| Number of pages | 7 |
| Journal | Journal of Biological Chemistry |
| Volume | 275 |
| Issue number | 10 |
| DOIs | |
| State | Published - 10 Mar 2000 |
Bibliographical note
Funding Information:José Eduardo Araújo. J.E. Araújo got his B.Sc. degree in Genetic and Biotechnology in 2012 and the M.Sc. in Comparative and Technologic Molecular Genetics in 2013, both at the University of Trás-os-Montes and Alto Douro (UTAD). In order to conclude his master degree and thesis he moved to the Bioscope research team ( www.bioscopegroup.org ) in 2012. Since then, he has developed competences and techniques applied to clinical proteomics, marine proteomics, computational and statistical proteomics. Since 2015, Mr. Araújo has been developing his Ph.D grant project awarded from the Portuguese Foundation of Science and Technology, at NOVA University of Lisbon. His CV comprises (up to August 2017), 11 published articles in international peer review journals, 13 congresses books and 21 posters and 5 oral communications presented. In addition, Mr. Araújo has worked and collaborated in 4 different project. Furthermore, he has been involved in the organization of 18 international conferences as member of the organizing committee. His current research areas are focused in (i) Biomarkers Discovery, (ii) Clinical Proteomics, (iii) Environmental Proteomics, (iv) Development of new bio-analytical methods for the study of the proteome using mass spectrometry with MALDI ionization, (v) application of 2D-gel electrophoresis to the proteome research and (vi) Application of fast sample treatment protocols for clinical proteomics research using ultrasonic devices.