Figure 2.

Changes in K_i or K_d (for binding of [³H]granisetron) as a result of alanine mutations. The values shown are the ratio of the K_d or K_i for wildtype and mutant receptors. The length of each bar illustrates the magnitude of change in either the K_d or K_i relative to wildtype while the direction indicates an increase (up) or decrease (down) in the K_d or K_i. A. Most alanine mutations produced little change in Kd. No binding was detected for the G147A and V149A receptors therefore no Kd could be determined. B. Changes in K_i were small for most receptors although large changes were observed for select ligands at Y140A, Y142A and Y152A receptors. The relative increases in K_i for these amino acids are as follows: 5-HT: Y140A 1.3 ± 0.30 fold, Y142A 110 ± 25 fold, Y152A 24 ± 5.6 fold mCPBG: Y140A 7.3 ± 1.7 fold, Y142A 160 ± 36 fold, Y152A 24 ± 5.6 fold d-tc: Y140A 50 ± 12 fold, Y142A 6.5 ± 1.5, Y152A 10.0 ± 2.3 fold lerisetron: Y140A 4.6 ± 1.1 fold, Y142A 160 ± 37 fold, Y152A 190 ± 43 fold