Aldehyde Tag (IMAGE) DOE/Lawrence Berkeley National Laboratory Caption DNA for the core sequence of six amino acids -- leucine, cysteine, threonine, proline, serine, and arginine (red letters) -- is cloned into the gene for the recombinant protein at the locus to be chemically modified. The cell's own FGE converts the cysteine in the sequence to formylglycine, outfitting the protein with an aldehyde group. Synthetic molecules (starred) that are specially equipped to react with the aldehyde group modify the protein at that site and no other. Many kinds of proteins can be tagged in this way; "generic" proteins are pictured here. Credit Carolyn Bertozzi laboratory, UC Berkeley, Lawrence Berkeley National Laboratory Usage Restrictions with credit as given License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.