The crystals measure one-tenth of one millimeter across and are built of iron-containing molecules called heme.
When malaria parasites infect human red blood cells and break down hemoglobin, the protein complex that transports oxygen, large amounts of heme are released into the blood stream. But free heme is toxic to the parasites, so they pack it into crystals to sequester its toxic reactivity.
The exact molecular composition of the particles has remained mysterious until recently.
When Jong Seto, PhD, adjunct faculty in UCSF’s Department of Biochemistry and Biophysics, first imaged these particles with a high-resolution electron microscope and saw tightly packed, beautiful crystals, he remembers thinking, “There’s something really regular going on here; this packing is not just by chance.”
Seto and his collaborator, Joe DeRisi, PhD, the Albert Bowers Endowed Chair in Biochemistry and the Gordon M. Tomkins Chair at UCSF, think that malaria parasites produce a protein that binds to heme and packs it into crystals. They have found candidate proteins in the malarial genome that resemble the iron-binding human protein ferritin.