Fatty Acid Desaturase Mutants of Yeast: Growth Requirements and Electron Spin Resonance Spin-Label Distribution

Bernadine J. Wisnieski, Richard K. Kiyomoto
1972 Journal of Bacteriology  
Two respiratory-sufficient and one respiratory-deficient (nuclear petite) strains of yeast A9-desaturase mutants were analyzed to determine which fatty acids would serve as replacements for the naturally occurring fatty acids, 16: 1 A" cis and 18: 1 A9 cis. The requirement can be satisfied by several fatty acids differing in double-bond position, steric configuration, chain length, and degree of unsaturation. The features common to growth-supporting fatty acids are presented and the effects of
more » ... arying the carbon source and temperature are considered. In addition, we illustrate several pitfalls encountered in membrane studies which exploit lipid-requiring organisms. Since the ipembrane fatty acid composition of these mutants can be modified readily, elec ron spin resonance spectroscopy is used to compare membranes of mutant strains enriched for different fatty acids. The lipid distribution pattern of the most commonly employed electron spin resonance spin-label, 12-nitroxide stearate, was ascertained and compared to that of 18: 1 A9 cis. Auxotrophic mutants affecting structural components provide valuable information on the relation between cellular structure and function. Prerequisite to research centering on the relevance of fatty acid composition to membrane structure, function, and biosynthesis is a knowledge of a mutant's fatty acid specificity. This study deals with the unsaturated fatty acid auxotrophs of yeast, olel and oIe2 (7, 14, 21) . Since these mutants are employed by several researchers interested in membrane phenomena, the present investigation aims to clarify a contradiction between earlier (21) and recent studies on KD115 (olel), and elucidates the distribution of the electron spin resonance (ESR) spin-labeled fatty acid analogue, 12-nitroxide stearate (12NS), into phospholipids, free fatty acids, and neutral lipids. MATERIALS AND METHODS Organisms. A wild-type strain of Saccharomyces cerevisiae, S288C (Berkeley Collection), and three fatty acid desaturase mutants derived from it were the organisms employed in this study. Two independent mutant isolates, olel-1 (KD115) and olel-2 (KD20), are respiratory-sufficient and heteroallelic. 'Present address:
doi:10.1128/jb.109.1.186-195.1972 fatcat:ctoahmsw7fg65mm3u4aj336yn4