Profile of Alexander D. Johnson.

Abstract

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). Alexander Johnson. Image courtesy of Trevor Sorrells. A metaphorical depiction of the messiness of transcription circuits as products of evolution rather than design. “Selection acts on the output, not the machinery,” says Johnson. Image courtesy of Nairi Hartooni and Trevor Sorrells. Born in Oak Ridge, Tennessee, in 1952, Johnson spent much of his childhood outdoors, especially after his father took a job as a science writer in State College, Pennsylvania. Johnson’s Boy Scout troop “didn’t emphasize advancement, uniform, or ceremony,” he says. “We just went.” There were monthly backpacking trips regardless of the weather, and he remembers canoeing the Susquehanna one March during a snowstorm. Still an active outdoorsman fifty years later, Johnson recently completed a 200-mile backpacking trip along the John Muir Trail in California with his nephews. During high school, Johnson, the son of two journalists, wrote for the school newspaper and the local paper, the Centre Daily Times . Later, when deciding on a career path, Johnson felt he had to choose between science and writing. “Little did I know that I would spend most of my time in science writing,” he says. He is now working with his coauthors on the sixth edition of the iconic …