Profile of Alexander D. Johnson.

Discussing the yeast Candida albicans, biochemist Alexander Johnson describes a resident of the human gut that can turn into a fatal pathogen in the immunocompromised. Johnson, a professor of microbiology and immunology at the University of California, San Francisco, appreciates the genetic intricacies of this eukaryote that changed his views on transcriptional regulation and the evolution of molecular circuitry. In his Inaugural Article, Johnson, elected to the National Academy of Sciences in 2011, combines biochemistry, genetics, and structural biology to reveal the structure of a highly conserved protein that regulates pathogenesis in a wide variety of fungi (1).