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Membrane fluidity alterations in a cytochrome P-450-deficient mutant of Candida albicans
N D Lees1, F W Kleinhans, M C Broughton
1Department of Biology, Indiana University-Purdue University, Indianapolis 46223.
Abstract:
A cytochrome P450-deficient mutant of the pathogenic fungus, Candida albicans, which accumulates exclusively 14 alpha-methylsterols in place of the normal end product sterol, ergosterol, was examined for alterations in membrane fluidity by electron paramagnetic resonance. The results using four nitroxyl spin labels indicated that exponential phase cultures of the mutant strain, D10, had a uniformly more rigid membrane than similarly grown wild type. Since D10 shows a sterol spectrum similar to that of wild type cells treated with imidazole and triazole antifungal agents, many of the physiological effects reported as the result of azole application may be the result of alterations in membrane fluidity.
Insights
A mutant Candida albicans fungus with altered sterol production exhibited a more rigid cell membrane. This finding suggests that changes in membrane fluidity may explain the physiological effects of azole antifungal drugs.
Area of Science:
- Mycology
- Biochemistry
- Cell Biology
Background:
- Candida albicans is a pathogenic fungus.
- Ergosterol is the primary sterol in C. albicans membranes.
- Cytochrome P450 enzymes are crucial for ergosterol biosynthesis.
Purpose of the Study:
- To investigate the impact of a cytochrome P450-deficient mutation on Candida albicans membrane fluidity.
- To compare the membrane properties of a mutant strain accumulating 14 alpha-methylsterols with wild-type cells.
Main Methods:
- Electron paramagnetic resonance spectroscopy was used to assess membrane fluidity.
- Four nitroxyl spin labels were employed to probe the membrane environment.
- Membrane fluidity was measured in exponential phase cultures of the mutant (D10) and wild-type strains.
Main Results:
- The D10 mutant strain displayed a uniformly more rigid cell membrane compared to the wild-type strain.
- The sterol profile of the D10 mutant was similar to wild-type cells treated with azole antifungal agents.
- Accumulation of 14 alpha-methylsterols in the mutant led to increased membrane rigidity.
Conclusions:
- Altered sterol composition in Candida albicans significantly impacts membrane fluidity.
- Increased membrane rigidity in the mutant strain suggests a mechanism for azole antifungal drug action.
- Changes in membrane fluidity may underlie many physiological effects observed with azole treatment.