Springer Online Journal Archives 1860-2000
Abstract A homogenous preparation of carboxysomes was isolated from Thiobacillus neapolitanus by means of density gradient centrifugation and preparative electrophoresis through agarose. Analysis of the carboxysomes by denaturing sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) revealed the presence of 12–15 polypeptides. Approximately 62% of the total protein was found to consist of the large and small subunits of ribulose-1,5-bisphosphate carboxylase-oxygenase (RubisCO). Two polypeptides were found to be components of the carboxysome shell. Ribose-5-phosphate isomerase, ribulose-5-phosphate kinase, and fructose-1,6-bisphosphatase could not be detected in the carboxysome. Purified carboxysomal and cytoplasmic RubisCO were shown to be similar if not identical by several criteria including specific activity, carboxylase/oxygenase activity, and electrophoretic mobility.
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