ISSN:
0091-7419
Keywords:
calcium transport
;
quinacrine fluorescence
;
rubidium transport
;
sucrose transport
;
lipopolysaccharide antibody
;
scanning electron microscopy
;
topology
;
membrane vesicles
;
Azotobacter vinelandii
;
Life Sciences
;
Molecular Cell Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
Notes:
Membrane vesicles were prepared from Azotobacter vinelandii spheroplasts by lysis in either potassium phosphate (pH 7.0) or Tris1-acetate (pH 7.8) buffers. These 2 types of preparations differ considerably in their properties: (1) Examination by scanning electron microscopy reveals that the Pi vesicles consist primarily of closed structures 0.6-0.8 μm in diameter with a rough or particulate surface similar to that of spheroplasts. The Tris vesicles are significantly smaller, 0.1-0.3 μm in diameter, and have a much smoother surface structure. (2) Antisera from rabbits immunized with A. vinelandii lipopolysaccharide antigen will agglutinate Pi vesicles but not Tris vesicles. (3) Tris vesicles have a fourfold higher specific activity of latent H+-ATPase than Pi vesicles. After exposure to Triton X-100 similar ATPase activities are observed for both types of vesicles. (4) Pi vesicles transport calcium in the presence of ATP or lactate at less than 30% of the rates observed for Tris vesicles. (5) Tris vesicles have less than 22% of the transport capacity of Pi vesicles for accumulation of labeled sucrose and less than 3% of the capacity for valinomycin-induced uptake of rubidium observed during respiration. (6) Quinacrine fluorescence intensity is reduced by 30% during lactate oxidation and 20% during ATP hydrolysis by Tris vesicles. Under similar conditions, fluorescence in Pi vesicles is quenched by only 7% and less than 2%, respectively. These findings suggest that Pi vesicles have the normal orientation of the intact cell whereas Tris vesicles have an inverted topology.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jss.400060306
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