INFLUENCE OF CLINOSTAT ROTATION ON PLANT-PROTEINS .2. EFFECTS ON MEMBRANE-BOUND ENZYME-ACTIVITIES AND UBIQUITIN-PROTEIN-CONJUGATES IN LEAVES OF VICIA-FABA L

Membrane-bound enzyme activities in microsomal membrane fractions and the ubiquitin-protein-conjugate pattern of Vicia faba L. extracts were analyzed after clinostat treatment for 15 and 24 h and compared with a vertically rotated control. The activity of vanadate-sensitive ATPas e was enhanced by clinostat treatment. The effect could be found in ex tracts of the youngest, not fully expanded leaves after 24 h of treatm ent, but as well as after 15 h of rotation and in primary leaf extract s. In addition, 24 h of clinostat rotation led to an increase in nitra te-sensitive ATPase activity and Antimycin A-insensitive NADH-cytochro me c reductase activity. No difference in latent IDPase activity was o bserved. The ubiquitin-protein-conjugate pattern of total cellular pro tein was changed by 24 h of clinostat treatment as revealed by SDS-PAG E and western-immunoblot analysis. The results indicate that the membr ane system of leaf cells is influenced by omnilateral gravistimulation . Similar to the soluble and thylakoid membrane proteins an altered ub iquitination pattern points to a changed protein turnover.