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|Title:||Phospholipid Transfer Protein Activity in Rhodopseudomonas Sphaeroides|
|Department / Program:||Microbiology|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||A protein capable of transferring phospholipid between membranes has been purified from photosynthetic cells of Rhodopseudomonas sphaeroides. When compared to the crude cell lysate, this phospholipid transfer protein has been purified approximately 1,400-fold with a recovery of 12.5%. The active protein is a globular monomer having a molecular weight of 27,000 and an isoelectric point of 5.2. This protein can transfer all phospholipid species tested with the order of efficiency of transfer being phosphatidylglycerol > phosphatidylcholine > phosphatidylethanolamine. Based on the differences in binding to phenyl-sepharose and in isoelectric point, there apparently are at least two different phospholipid transfer proteins in the cell lysate.
Phospholipid transfer protein activity can be detected in the cell lysates of photosynthetically, as well as chemoheterotrophically, grown R. sphaeroides. Cells growing under different growth conditions have different amounts of the phospholipid transfer protein activity and this difference may merely reflect the difference in growth rate of the cells. Studies employing synchronous cultures show that the level of the phospholipid transfer activity is directly proportional to the cell number of the culture. The increase of specific activity of the phospholipid transfer activity is coincident with the increase in cell number and with the event of transferring phospholipid into the intracytoplasmic membrane during the cell cycle. It is possible that rapidly dividing cells may require an increased level of phospholipid transfer activity in order to satisfy their requirement for membrane synthesis.
The distribution of phospholipid transfer activity between soluble and membrane-associated forms is affected by the cellular growth conditions. Low light grown cells have the highest amount of intracytoplasmic membrane as well as the fraction of membrane-associated phospholipid transfer activity. The whole cell phospholipid transfer activity is further localized into periplasmic and cytoplasmic fractions.
The physiological role of the phospholipid transfer protein is suggested to be involved in intermembrane phospholipid translocation and in membrane lipid metabolism, lipid turnover or the modulation of the activities of membrane-associated proteins.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1985.
|Date Available in IDEALS:||2014-12-16|