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JBC, Vol. 250, Issue 18, 7173-7181, Sep, 1975
S. C. Hubbard and S. Brody
The glycerophospholipids of cultures of Neurospora crassa were extracted,
deacylated, and analyzed. In addition to a wild-type strain, several
auxotrophic mutant strains were examined: chol-1 (defective
S-adenosylmethionine: phosphatidylethanolamine methyltransferase), chol-2
(defective S-adenosyl methionine:phosphatidylmonomethylethanolamine
(dimethylethanolamine) methyltransferase), and inos (defective
myoinositol-1-phosphate phosphatase). In addition, a double mutant strain,
chol-1;chol-2, was constructed. Cultures of the mutant strains grown with
concentrations of supplement(s) just adequate to support growth had bizarre
phospholipid compositions. By appropriate choice of mutant and
supplement(s), it was possible to vary the relative level of every
phospholipid of the organism, with the exception of cardiolipin. The
maximum ranges encountered for the zwitterionic species, expressed as per
cent of total phospholipid phosphorus, were lecithin (0.9 to 53.1%),
phosphatidyldimethylethanolamine (0.0 to 55.5%),
phosphatidylmonomethylethanolamine (0.0 to 53.9%), and
phosphatidylethanolamine (9.8 to 43.3%). For the anionic species, the
ranges were phosphatidylserine (1.7 to 10.4%) and phosphatidylinositol (3.6
to 25.1%). Despite the wide variation of the relative proportions of the
individual phospholipid species, five quantities remained constant: the
cardiolipin content, the total phospholipid content, the total content of
the zwitterionic species, the total content of the anionic species, and the
ratio of the zwitterionic to anionic totals. The data suggest the existence
of an internal compensation mechanism, the net effect of which is
maintenance of a fairly constant contribution by the phospholipid
components to the over-all membrane charge.
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