The five most proximal C-terminal amino acids (C-term.), the specific linker sequences introduced during concatenation (Linker sequence), and the five first amino acids from the predicted mature N terminus (N-term.) are presented for the indicated subunit pairs. Total-linker-lengths (Sum) are calculated as the sum of all existing amino acids and introduced linker sequence between two artificial fix points “End TM4” and “Anchor.” The five most proximal amino acids in TM4 (End TM4) and C-terminal tail lengths (C-tail) are obtained from UniProt (P14867 for α1 and P47870 for β2). The N-terminal lengths (N-term. to Anchor) are derived from a definition of an α-helix 1 anchor (Anchor) as described in the text. For tetrameric and pentameric constructs, numbers in superscript indicate the construct position of each subunit (e.g., β2^second: β2 subunit in the second construct position).