Glutamic acids within LR enhance the MRIP-binding affinity.

<p><b>(A)</b> Amino acid sequences of the wild-type LR (WT-LR) and mutant LR peptides. Charged residues are in bold, the leucine repeat is in Italic, and substitution mutations are underlined. <b>(B)</b> Time derivative s*lg(s*) graphs: Line, MRIP^724-878 alone (50 μM); filled-in circles, original mixture of MRIP^724-878/each mutant LR peptide (50 μM each except for R992D/R993D and E996K whose mixtures consisted of excess amount of the mutant LR peptides); open circles, a three-fold dilution of the original mixture. The molar mass of the complex differs slightly from that of MRIP^724-878 dimer (37.9 kDa vs 37.4 kDa), and thus the shift in the main peak position is not easily discernable in many cases.