(A) To identify functional receptor TMDs and JMDs for modular assembly, 88 TMDs and 76 JMDs were cloned into a human synNotch scaffold, replacing either the Notch1 TMD or JMD, respectively. Jurkat T cells expressing an inducible BFP reporter were transduced with these SNIPR libraries in an arrayed format. (B) Normalized results of TMD screening in Jurkat T cells. An alignment of the best performing TMDs shows a common Gly-Val motif (Dark blue = >80% agreement with consensus sequence, blue = >60% agreement, light blue = >40% agreement). An alanine scan of the human Notch1 TMD in primary T cells supports the importance of this motif. (C) Same as B, but with the JMD library. High-performing JMDs are strongly basic at their N-termini and may include polar residues but not acidic or hydrophobic residues. (D) Compared to a reference SNIPR containing the Notch1 TMD/JMD, a SNIPR containing the CLSTN2 TMD/JMD is inactive, but receptor function is restored when the CLSTN2 JMD is replaced with the Notch1, AGER or PTPRF JMD.