Thermostability of GIM-1 and mutants. Fluorescence signals are for wild-type GIM-1 and the W228R, W228A, W228Y, W228S, Y233N, Y233A, Y233I, and Y233S mutants. Mean ± standard deviation melting temperatures are given in parentheses. The assay was performed in 50 mM HEPES (pH 7.2).