A model showing the structure of the human transferrin proteinWIKIMEDIA, EMWDamaging toxins and antibody-epitope interactions are frequently the battlegrounds of host-pathogen arms races, but a new study suggests a role for a different, so-called “nutritional” immune system. In primates, the iron-carrying protein transferrin likely evolved to inhibit meningitis-causing bacteria from scavenging iron, an essential but limited nutrient, researchers reported last week (December 11) in Science.
Matthew Barber and Nels Elde from the University of Utah School of Medicine compared transferrin-encoding genes from 21 primate species, and found remarkable variation at sites known to interact with a bacterial transferrin binding protein, TbpA. Two bacterial species, Haemophilus influenzae and Neisseria meningitidis, are among the main causes of meningitis, a life-threatening inflammation of the membranes surround the brain and spinal cord.
“Transferrin was acting as if it was an immunity gene,” Elde told National Geographic’s Not Exactly Rocket Science. A protein with such a basic function might be expected to remain relatively stable over evolutionary time. But Barber and Elde found that one of the protein’s two lobes had undergone rapid changes that did not affect its ability to bind iron. The changes ...
