Fig. 3: C-4 demethylation in E. salina.
a Total ion chromatograms showing lanosterol (I) substrate production in our E. coli heterologous expression system. b Co-expression of SdmAB homologs from E. salina, resulting in production of only a 4-methylaldehyde intermediate (III). These two enzymes are insufficient to demethylate at C-4, distinguishing them from SdmAB homologs in aerobic methanotrophs. c Co-expression of SdmAC homologs from E. salina, resulting in removal of single methyl group at C-4. d Co-expression of SdmABC homologs from E. salina, resulting complete demethylation at C-4. Lipids were derivatized to trimethylsilyl groups. C-4 demethylation intermediates were confirmed in a previous study and identified here by comparison to published mass spectra (32). Mass spectra of identified sterols are shown in Supplementary Fig. 9. Source data are provided as a Source Data file.
