Posttranslational mutagenesis: A chemical strategy for exploring protein side-chain diversity

Radicals push proteins beyond genes Chemically modifying proteins after their translation can expand their structural and functional roles (see the Perspective by Hofmann and Bode). Two related methods describe how to exploit free radical chemistry to form carbon-carbon bonds between amino acid residues and a selected functional group. Wright et al. added a wide range of functional groups to proteins containing dehydroalanine precursors, with borohydride mediating the radical chemistry. Yang et al. employed a similar approach, using zinc in combination with copper ions. Together, these results will be useful for introducing functionalities and labels to a wide range of proteins. Science , this issue pp. 597 and 623 ; see also p. 553