Desensitization and deactivation differences are not specified by TM2. A, Desensitization and deactivation kinetics of receptors containing TM2 “swapped” subunits. The four divergent residues of TM2 shown in (B) have been exchanged in each subunit as indicated in the schematics. Neither desensitization nor deactivation was altered by this exchange for either subunit. For comparison,shaded vertical bars represent the range of values (mean ± SEM) obtained for wild-type αβδ and αβγ receptors. Horizontal calibration: 400 msec; vertical calibration: 10 pA for δ(M2S), 285 pA for γ2L(M2S). B, Amino acid sequence alignment of the second transmembrane domains of the δ and γ2L subunits. N-terminal end (intracellular side) is to theleft. The δ sequence is A259 through R282; the γ2L sequence is A261 through R284. Identical residues shared by these subunits are shaded, including the 9′ leucine (see Results).