Composition of cell envelope
Springer Online Journal Archives 1860-2000
Abstract Envelope preparations of chemotrophically and phototrophically grown Rhodospirillum tenue were isolated and characterized on the basis of their contents and composition in phospholipids and fatty acids, as well as on the basis of their enzyme activities, absorption spectra and polypeptide patterns. Both preparations were similar in their contents in phospholipids and fatty acids. Their total fatty acids were characterized by a rather high percentage of saturated fatty acids. The activities of the respiratory reactions were considerably higher in chemotrophic than in phototrophic membranes. This is true especially for activities of the terminal oxidase which were over 20 times greater. The affinities of the corresponding enzymes to their respective substrates (K m ) differed with differences in the culture conditions. Under chemotrophic conditions the K m values for the NADH-dependent reactions were lower than those values under phototrophic conditions, whereas the K m values for the succinate dependent reactions were higher. The low temperature (77°K) near infrared spectrum of the phototrophic membrane showed a peak at 875 nm which was not detectable in the chemotrophic membrane. The polypeptide patterns, in the presence of sodium dodecyl sulfate, of both preparations were quite similar except for the presence of two low molecular weight proteins (M. Wt. 12,000 and 10,000) in the phototrophic membrane which were absent in the chemotrophic membrane. Both envelope preparations were further fractionated into enriched cytoplasmic membrane and outer membrane fractions which were identified on the basis of their contents in 2-keto-3-deoxyoctonate, ubiquinone 8 and bacteriochlorophyll (in the case of the phototrophic membrane) and their enzyme activities. The buoyant densities of the corresponding fractions from both envelope preparations were found to be equal. The data presented in this paper demonstrate that envelope preparations of chemotrophically and phototrophically grown R. tenue are similar in their contents in 2-keto-3-deoxyoctonate, ubiquinone 8, phospholipids and fatty acids, yet differ significantly in their spectra, protein patterns and enzyme activities.
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