Coating the outside of cells with oligomers and polymers of sialic acid sugar helps cells migrate, which is central to fetal brain development and adult memory formation. These polysialyl coats are also infamous for cancer cell metastasis; the negatively charged sugars packed on their exteriors help cancer cells eschew adhesion in favor of distant travel. A study that, for the first time, describes the atomic-level structure of a human polysialyltransferase, which attaches sialic sugars to the exterior of cells, may help researchers develop new anticancer agents and gain a deeper understanding of brain function (Nat. Struct. Mol. Biol. 2015, DOI: 10.1038/nsmb.3060). A team of scientists led by Gesa Volkers and Natalie Strynadka of the University of British Columbia, in Vancouver, used X-ray crystallography and other techniques to solve the structure with a resolution of 1.8 Å and to propose a mechanism for the enzyme’s catalytic activity. This particular polysialyltransferase, ST8SiaIII, is one of three found in humans, and its precise role is unknown, comments Laurence Patterson of the University of Bradford, in England. However, its similarity to the human polysialyltransferase known to be involved in cancer suggests the structure will be useful for drug research, he adds.