FIG 4.
Functional validation of the atranorin BGC. (A) A proposed biosynthetic pathway for atranorin. (B) HPLC profiles of culture extracts of a “clean host” expressing different sets of biosynthetic genes of the atranorin BGC: with no introduced gene (i), with atr1 only (ii), with atr1 and atr3 (iii), with atr1 and atr2 (iv), and with atr1, atr2, and atr3 (v). The acetone extract of an authentic voucher specimen for the genome-sequenced Stereocaulon alpinum contains atranorin (compound 5) and lobaric acid (tR = 33.1 min) (vi). (C) Extracted-ion chromatograms (EIC) with the indicated m/z values for compounds 1 to 6.