MICROSOMAL MEMBRANE-PROTEINS AND VANADATE-SENSITIVE ATPASE FROM VICIA-FABA ROOT-TIPS AFTER CLINOSTAT TREATMENT

Microsomal and soluble protein fractions from Vicia faba root tips wer e used for SDS-PAGE and Western-immunoblot analysis with anti-ubiquiti n antibodies after 9 h clinostat treatment of the plants. In contrast to soluble proteins omnilateral gravistimulation (9 h) resulted in an enhanced proteolytic capacity for microsomal proteins. The increase of vanadate-sensitive ATPase activity was 83% after 9h clinostat treatme nt, when the enzyme activity was measured directly after membrane prep aration. Enhanced ATPase activity was correlated with the appearance o f a polypeptide of about 100 kDa and its fragments (93 and 80 kDa). AT Pases are not the only membrane bound proteins, which are changed duri ng clinostat treatment, as several ubiquitinated polypeptides were als o affected. A 1 h storage of microsomal fractions led to a shift of ba nd intensities on ubiquitin-specific Western-blots. The demonstrated e ffect could not be observed, when fractions were isolated in the prese nce of protease inhibitors. In accordance with the polypeptide analysi s omnilateral gravistimulation resulted in an enhanced capacity to deg rade specific microsomal ubiquitin-conjugates, whereas the soluble ubi quitin-pool was not visibly affected.