The bacterium Salmonella Typhi causes typhoid fever in humans, but leaves other mammals unaffected. Researchers at University of California, San Diego and Yale University Schools of Medicine now offer one explanation — CMAH, an enzyme that humans lack. Without this enzyme, a toxin deployed by the bacteria is much better able to bind and enter human cells, making us sick. The study is published in the journal Cell.
Due to a single oxygen atom difference in sialic acids, typhoid toxin affects humans while other mammals are resistant.
Credit: UC San Diego School of Medicine
Co-authors include Lingquan Deng, Nissi Varki, Yuko Naito-Matsui, UC San Diego School of Medicine; Jeongmin Song, Xiang Gao, Yale University School of Medicine; Jiawei Wang, Tsinghua University; Hai Yu, Xi Chen, University of California, Davis.
This research was funded, in part, by the National Cancer Institute (grant CA38701) and the National Institute of Allergy and Infectious Diseases (grant AI079022), both part of the U.S. National Institutes of Health.