Appending the Sly1 loop to the amino terminus of Sly1∆loop partially restores function. (A) Chimeric constructs were prepared with different fragments of the Sly1 loop appended to the N-terminus of Sly1 via a short, flexible linker (see Table S3 for details). Mutants designated pα21 had the five polar substitutions in the appended loop as described in Fig. 6 C. (B) The loop-Sly1 mutants were expressed from the native SLY1 promoter on single-copy plasmids. Growth of a sly1∆ strain was assessed in the presence of the indicated constructs following ejection of a SLY1 balancer plasmid by plating on media containing 5-FOA. (C–F) Fusion driven by mutants with fragments of the loop (C and E) or polar derivatives of the same fragments (D and F). Points show mean ± SEM of three independent experiments; in many cases the error bars are smaller than the symbols. Gray lines show least-squares nonlinear fits of a second-order kinetic model.