A radically different enzyme

摘要

One of the ways in which biology extends the functionality and reactivity of the naturally occurring amino acids that make up proteins is by modifying the proteins after their synthesis on the ribosome, a process known as post-translational modification. Some enzymes catalyse their own modifications, but one or more separate enzymes are sometimes used for this purpose. On page 891 of this issue, Zhang et al.report their findings on the post-translational modification of translation elongation factor 2 (EF2), a factor that is crucial for protein synthesis on the ribosome. This modification generates a structure known as diphthamide, so called because it is the target of the diphtheria toxin. The authors find that the modification is carried out by the Dph2 enzyme in an unprecedented reaction using free radicals, and that a cluster of iron and sulphur atoms in the enzyme is involved.