Specific residues in the N terminus contribute to degradation rate, whereas rate determinants in the C terminus are not necessarily sequence specific. A to C, Ala substitution (white circles) of the KR rate motif residues within the NdC fragment (dark-blue) in IAA17 (A) and IAA1 (B) slowed degradation similar to the dC fragment (light-blue), whereas Ala substitution of the KQ residues of IAA28 (C) had no effect on degradation dynamics. D, Replacing the IAA28 KQ with KR (white circles) did not affect half-life but promoted more complete degradation of the Nd fragment (orange). E, Shortening the distance between the IAA17 degron and the KR rate motif by either moving the KR forward 25 residues (diamonds) or deleting 25 residues (triangles) did not lead to faster degradation of IAA17.Nd. F, The C-terminal rate motif of IAA28 displayed no obvious sequence specificity. Ala substitutions and polar→nonpolar mutations (white symbols) of the nine residues immediately terminal of the degron in the IAA28.dC* fragment (bright-blue) had weak effects on degradation. G, Half-lives with 95% confidence intervals for data in A to F. WT, Wild type.