Lanmodulin orthologs with improved rare earth separation performance

A protein having an enhanced REE/REE selectivity, comprising a first EF hand motif, a second EF hand motif, a third EF hand motif, and a fourth EF hand motif, each EF hand motif comprising 11, 12, or 14 amino acid residues, wherein when the first EF hand motif, the second EF hand motif, the third EF hand motif, and the fourth EF hand motif have 12 amino acid residues, each EF hand motif has the following sequence:

• wherein,
• i) for the first EF hand motif and the fourth EF hand motif:
• each X1 is independently D or N;
• each X2 is independently any canonical amino acid;
• each X3 is independently D, N, or E;
• each X4 is independently any canonical amino acid;
• each X5 is independently D, N, or E;
• each X6 is independently any canonical amino acid;
• each X7 is independently any canonical amino acid;
• each X8 is independently a hydrophobic residue;
• each X9 is independently a D, E, or T;
• each X10 is independently a hydrophobic residue;
• and
• each X11 is independently any canonical amino acid;
• ii) for the second EF hand motif:
• X1 is N;
• X2 is any canonical amino acid;
• X3 is D;
• X4 is any canonical amino acid;
• X5 is D;
• X6 is any canonical amino acid;
• X7 is T or S;
• X8 is a hydrophobic residue;
• X9 is E;
• X10 is any canonical amino acid;
• and
• X11 is any canonical amino acid;
• and
• iii) for the third EF hand motif:
• X1 is D;
• X2 is any canonical amino acid;
• X3 is D;
• X4 is D;
• X5 is D;
• X6 is G;
• X7 is T or S;
• X8 is a hydrophobic residue;
• X9 is D;
• X10 is any canonical amino acid;
• and
• X11 is any canonical amino acid;
• iv) at least one X2 of the second EF hand motif and third EF hand motif is P;
• and
• v) the EF hand motifs are connected by 12 or 13 amino acid residue linkers, wherein each amino acid of the linkers is a canonical amino acid and at least one amino acid of any of the linkers are hydrophobic.