Figure 9.

Binding of α-factor to Ste2p. Glutamine (Q¹⁰) of the C-terminus of α-factor binds to residues Ser47 and Thr48 at the interface of the receptor’s N-terminus and the extracellular face of TM1 and tyrosine (Y¹³) binds to Arg58 and/or Cys59 in TM1. The bending of the pheromone around the loop region facilitates the interaction between the tryptophan (W¹) at the N-terminus of α-factor and residues Y266 and K269 in TM6 and EL3. The N-terminus is shown interacting with EL1. α-Factor residues are indicated in black (not all the residues of the pheromone are shown in the figure), Ste2p residues are shown in blue, Ste2p loops and termini are in red, and transmembrane domains are in gray.