Designed by: Lena Schorr   Group: iGEM19_FAU_Erlangen   (2019-10-18)

scFv against CD3 with SpyTag codon optimized for E.coli

BBa_K3117048 is a fusion protein of an anti-CD3 single-chain variable fragment (scFv) and SpyTag (BBa_K3117037). This part is codon optimized for the expression in E.coli.

Usage and Biology

By connecting the variable regions of the heavy and the light chain of an anti-CD3 antibody with a short GGGGS linker (BBa_K3117004), the scFv retains it's antigen-binding ability and is much smaller than a conventional antibody. Thus, it is well suited as part of a fusion protein with another effector. The SpyTag attached to the scFv belongs to the SpyTag/SpyCatcher system and is one part of the FbaB protein of Streptococcus pyogenes. Once it comes into contact with its corresponding other part, the SpyCatcher (BBa_K3117038), they bind covalently. This allows our part to be used in a modular manner in combination with other molecules carrying the SpyCatcher. The sequence contains a C-terminal His-tag (BBa_K3117006) for easy purification and detection. Secretion of the protein is ensured by an Igk leader. When the protein passes the membrane, this leader segment is cleaved off.

Our part targets CD3 on T lymphocytes, and thereby activates them. The most prominent effect of such activation is the release of cytotoxic granula into the environment of the cell. T cells play an integral part in the immune system of the body and are e.g. tasked with the identification and destruction of aberrant cells. Anti-CD3 antibodies are therefore a major tool in cancer research and also in cancer therapy (Ellerman, 2019).

By providing a modular platform, our part can be used in combination with a large variety of effector molecules and other antibodies to further evaluate the therapeutic potential of this application.


1. Ellerman, D. (2019). Bispecific T-cell engagers: Towards understanding variables influencing the in vitro potency and tumor selectivity and their modulation to enhance their efficacy and safety. Methods, 154, 102-117.