Peptide chemical ligation inside living cells: In vivo generation of a circular protein domain

Here we describe the first example of a peptide chemical ligation reaction performed inside a living cell. A cell-based native chemical ligation appro ach was developed and used to generate a circular version of the N-terminal Src homology 3 (SH3) domain from the murine c-Crk adapter protein inside E scherichia coli cells. The in vivo cyclization reaction was extremely effic ient and the resulting circular protein domain was fully biologically activ e and able to adopt the native SH3 folded structure. This work represents a n important step towards the in vivo generation of small backbone cyclic pe ptides for use in basic biological research. (C) 2001 Elsevier Science Ltd. All rights reserved.