Evolutionarily conserved Δ25(27)-olefin ergosterol biosynthesis pathway in the alga Chlamydomonas reinhardtii

Matthew B. Miller, Brad A. Haubrich, Qian Wang, William J. Snell, W. David Nes

Research output: Contribution to journalArticle

27 Citations (Scopus)

Abstract

Ergosterol is the predominant sterol of fungi and green algae. Although the biosynthetic pathway for sterol synthesis in fungi is well established and is known to use C24-methylation-C24 (28)-reduction (Δ24(28)-olefin pathway) steps, little is known about the sterol pathway in green algae. Previous work has raised the possibility that these algae might use a novel pathway because the green alga Chlamydomonas reinhardtii was shown to possess a mevalonate-independent methylerythritol 4-phosphate not present in fungi. Here, we report that C. reinhardtii synthesizes the protosterol cycloartenol and converts it to ergosterol (C24β-methyl) and 7-dehydroporiferasterol (C24β-ethyl) through a highly conserved sterol C24- methylation-C25- reduction (Δ25(27)-olefin) pathway that is distinct from the well-described acetate-mevalonate pathway to fungal lanosterol and its conversion to ergosterol by the Δ24 (28)-olefin pathway. We isolated and characterized 23 sterols by a combination of GC-MS and proton nuclear magnetic resonance spectroscopy analysis from a set of mutant, wild-type, and 25-thialanosterol-treated cells. The structure and stereochemistry of the final C24-alkyl sterol side chains possessed different combinations of 24β-methyl/ethyl groups and Δ22(23) E and Δ25 (27)-double bond constructions. When incubated with [methyl-2H3]methionine, cells incorporated three (into ergosterol) or five (into 7-dehydroporiferasterol) deuterium atoms into the newly biosynthesized 24β-alkyl sterols, consistent only with a Δ25 (27)-olefin pathway. Thus, our findings demonstrate that two separate isoprenoid-24-alkyl sterol pathways evolved in fungi and green algae, both of which converge to yield a common membrane insert ergosterol.

Original languageEnglish (US)
Pages (from-to)1636-1645
Number of pages10
JournalJournal of Lipid Research
Volume53
Issue number8
DOIs
StatePublished - Aug 2012

Fingerprint

Ergosterol
Chlamydomonas reinhardtii
Biosynthesis
Alkenes
Sterols
Algae
Chlorophyta
Fungi
Mevalonic Acid
Methylation
Lanosterol
Stereochemistry
Die casting inserts
Deuterium
Biosynthetic Pathways
Terpenes
Methionine
Nuclear magnetic resonance spectroscopy
Acetates
Magnetic Resonance Spectroscopy

Keywords

  • Cycloartenol
  • Green algae
  • Membranes
  • Sterol C24-methyl transferase
  • Sterol C25-reductase
  • Sterol evolution

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology
  • Endocrinology

Cite this

Evolutionarily conserved Δ25(27)-olefin ergosterol biosynthesis pathway in the alga Chlamydomonas reinhardtii. / Miller, Matthew B.; Haubrich, Brad A.; Wang, Qian; Snell, William J.; Nes, W. David.

In: Journal of Lipid Research, Vol. 53, No. 8, 08.2012, p. 1636-1645.

Research output: Contribution to journalArticle

Miller, Matthew B. ; Haubrich, Brad A. ; Wang, Qian ; Snell, William J. ; Nes, W. David. / Evolutionarily conserved Δ25(27)-olefin ergosterol biosynthesis pathway in the alga Chlamydomonas reinhardtii. In: Journal of Lipid Research. 2012 ; Vol. 53, No. 8. pp. 1636-1645.
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AB - Ergosterol is the predominant sterol of fungi and green algae. Although the biosynthetic pathway for sterol synthesis in fungi is well established and is known to use C24-methylation-C24 (28)-reduction (Δ24(28)-olefin pathway) steps, little is known about the sterol pathway in green algae. Previous work has raised the possibility that these algae might use a novel pathway because the green alga Chlamydomonas reinhardtii was shown to possess a mevalonate-independent methylerythritol 4-phosphate not present in fungi. Here, we report that C. reinhardtii synthesizes the protosterol cycloartenol and converts it to ergosterol (C24β-methyl) and 7-dehydroporiferasterol (C24β-ethyl) through a highly conserved sterol C24- methylation-C25- reduction (Δ25(27)-olefin) pathway that is distinct from the well-described acetate-mevalonate pathway to fungal lanosterol and its conversion to ergosterol by the Δ24 (28)-olefin pathway. We isolated and characterized 23 sterols by a combination of GC-MS and proton nuclear magnetic resonance spectroscopy analysis from a set of mutant, wild-type, and 25-thialanosterol-treated cells. The structure and stereochemistry of the final C24-alkyl sterol side chains possessed different combinations of 24β-methyl/ethyl groups and Δ22(23) E and Δ25 (27)-double bond constructions. When incubated with [methyl-2H3]methionine, cells incorporated three (into ergosterol) or five (into 7-dehydroporiferasterol) deuterium atoms into the newly biosynthesized 24β-alkyl sterols, consistent only with a Δ25 (27)-olefin pathway. Thus, our findings demonstrate that two separate isoprenoid-24-alkyl sterol pathways evolved in fungi and green algae, both of which converge to yield a common membrane insert ergosterol.

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