Abstract: The present invention relates to an isolated polypeptide comprising at least one intein or at least one intein fragment of said intein, wherein said intein is a naturally split intein with a N-terminal intein fragment split after 14-60 amino acids from the intein's N-terminal end and methods of using the same.

Abstract: The invention provides methods of producing functional split inteins having small N-intein and/or small C-intein. Using these split inteins with their protein trans-splicing and cleavage activities, we provide new and more effective methods of manipulating proteins. They include site-specific addition of synthetic peptides at protein's terminal and internal locations, ligation of synthetic and/or expressed polypeptides, controllable cyclization of synthetic and/or expressed polypeptides, and controllable cleavages of recombinant proteins. These methods have numerous utilities including but not limited to protein fluorescence labeling, fixation on microchips, site-specific PEGylation, and linkage with pharmaceutical molecules.

Abstract: The invention provides methods of producing functional split inteins having small N-intein and/or small C-intein. Using these split inteins with their protein trans-splicing and cleavage activities, we provide new and more effective methods of manipulating proteins. They include site-specific addition of synthetic peptides at protein's terminal and internal locations, ligation of synthetic and/or expressed polypeptides, controllable cyclization of synthetic and/or expressed polypeptides, and controllable cleavages of recombinant proteins. These methods have numerous utilities including but not limited to protein fluorescence labeling, fixation on microchips, site-specific PEGylation, and linkage with pharmaceutical molecules.