Fig. 7.

Leu¹⁷³ in hFFA2-eYFP is required for 4-CMTB allosterism but not agonism. A Leu¹⁷³Ala mutation was introduced into the 2nd extracellular loop of hFFA2-eYFP, and this inducible construct was expressed stably in Flp-In TREx 293 cells. A, [³⁵S]GTPγS incorporation in response to either propionate (pEC₅₀ = 3.95 ± 0.15) or 4-CMTB (pEC₅₀ = 6.14 ± 0.06) is unaffected by L¹⁷³A mutation within hFFA2-eYFP. B, coincubation of L¹⁷³A hFFA2-eYFP with fixed concentrations of 4-CMTB and varying amounts of propionate no longer resulted in a significant shift in the potency of propionate, indicated by the arrow. n.s., not significant according to one-way ANOVA. C, the loss of allosterism was reciprocal, with no significant difference in pEC₅₀ range indicated by the arrow. n.s., not significant according to one-way ANOVA. Data are mean ± S.E.M (n = 3) in each panel.