= Solution
The \b[S61/E62 and S75/Q76 pairs] are especially important for the extra stimulation attributable to <Munc18>. Their replacement leaves basal lipid mixing broadly present but makes the red and blue traces much closer together. In contrast, replacement of R47/V48 or D57/Q58 retains strong stimulation. The S75/E78/T79 replacement retains a smaller enhancement, suggesting a partial contribution under these conditions.
Compare the Munc18-dependent increment with each construct's own baseline, rather than comparing red endpoints alone. These results identify functionally important regions; they do not prove that every altered side chain directly contacts <Munc18>. The original reconstitution experiments also support cognate-SNARE recognition.<Selective activation of cognate SNAREpins by Sec1-Munc18 proteins by Jingshi Shen and others>[v-SNARE-dependent specificity of Munc18 stimulation]{ref}
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