Mode of uptake of sterol by Arthrobacter simplex |
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Authors: | Rajkhowa RC Goswami Pranab Singh HD |
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Institution: | (1) Department of Zoology, Cotton College, Guwahati, 781 001 Assam, India;(2) Department of Biochemistry, Regional Research Laboratory, Jorhat, 785 006 Assam, India;(3) Department of Biochemistry, Manipur University, Imphal, 795 003 Manipur, India |
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Abstract: | The mechanism of uptake of water-insoluble -sitosterol by a newly isolated strain of Arthrobacter
simplex SS-7 was studied. The production of an extracellular sterol-pseudosolubilizing protein during growth of A. simplex on -sitosterol was demonstrated by isolating the factor from the cell-free supernatant and its subsequent purification by Sephadex G-150 column chromatography. The M
r of the purified sterol-pseudosolubilizing protein determined by SDS–PAGE was 19kDa. The rate of sterol pseudosolubilization (5.2×10–3g l–1h–1) could not adequately account for the rate of sterol uptake (72×10–3g l–1h–1) and the specific growth rate (56×10–3 h–1). However in the unfavourable growth condition, when the cells were treated with sodium azide at the level of 30–60% of MIC, the sterol pseudosolubilization accounted for nearly 74% of the total growth containing 96% free cells. Cellular adherence to substrate particles was found to play an active role in the normal growth of the strain on -sitosterol. Unlike sodium acetate-grown cells, whose surface activity was negligible (60mNm–1), the sterol-grown cells had strong surface activity (40mNm–1). The high lipid content and long chain fatty acids in the cell-wall of -sitosterol-grown cells probably contribute to the high sterol adherence activity of the cells. |
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Keywords: | A simplex cell-surface pseudosolubilization -sitosterol" target="_blank">gif" alt="beta" align="MIDDLE" BORDER="0">-sitosterol |
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