Localization in Sucrose Gradients of the Pyrophosphate-Dependent Proton Transport of Maize Root Membranes
AUTOR(ES)
Chanson, Alain
RESUMO
A maize (Zea mays L. cv LG 11) root homogenate was prepared and centrifuged to sediment the mitochondria. The pellet (6 KP) and the supernatant (6 KS) were collected and fractionated on linear sucrose density gradients. Marker enzymes were used to study the distribution of the different cell membranes in the gradients. The distribution of the ATP- and pyrophosphate-dependent proton pumping activities was similar after 3 hours of centrifugation of the 6 KS or the 6 KP fraction. The pumps were clearly separated from the mitochondrial marker cytochrome c oxidase and the plasmalemma marker UDP-glucose-sterolglucosyl-transferase. The pyrophosphate-dependent proton pump might be associated with the tonoplast, as the ATP-dependent pump, despite the lack of a specific marker for this membrane. However, under all the conditions tested, the two pumps overlapped the Golgi markers latent UDPase and glucan synthase I and the ER marker NADH-cytochrome c reductase. It is therefore not possible to exclude the presence of proton pumping activities on the Golgi or the ER of maize root cells. The two pumps (but especially the pyrophosphate-dependent one) were more active (or more abundant) in the tip than in the basal part of maize roots, indicating that these activities might be important in growth processes.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1056791Documentos Relacionados
- Proton Transport in Maize Tonoplasts Supported by Fructose-1,6-Bisphosphate Cleavage. Pyrophosphate-Dependent Phosphofructokinase as a Pyrophosphate-Regenerating System1
- Localization of dolichyl phosphate- and pyrophosphate-dependent glycosyl transfer reactions in Saccharomyces cerevisiae.
- Purification and characterization of pyrophosphate-dependent phosphofructokinase from phosphate-starved Brassica nigra suspension cells.
- Pyrophosphate-dependent phosphofructo-1-kinase complements fructose 1,6-bisphosphatase but not phosphofructokinase deficiency in Escherichia coli.
- Regulation of pea seed pyrophosphate-dependent phosphofructokinase: Evidence for interconversion of two molecular forms as a glycolytic regulatory mechanism