Disclosed is method of engineering an immunobinder, the immunobinder comprising a human Vk3 family light chain variable region, or fragment thereof, the Vk3 family light chain variable region comprising VL framework residues, the method comprising: A) selecting one or more amino acid positions within the Vk3 framework residues and B) mutating the one or more amino acid positions selected for mutation, wherein the mutating comprises one or more substitutions selected from the group consisting of: wherein if the one or more light chain amino acid positions selected for mutation are of a human Vk3 family light chain variable region, the mutating comprises one or more substitutions selected from the group consisting of: (i) isoleucine (I) at amino acid position 10 using AHo or Kabat numbering system (ii) tyrosine (Y) at amino acid position 12 using AHo or Kabat numbering system (iii) serine (S) at amino acid position 18 using AHo or Kabat numbering system (iv) alanine (A) at amino acid position 20 using AHo or Kabat numbering system (v) methionine (M) at amino acid position 56 using AHo numbering system (amino acid position 48 using Kabat numbering system) (vi) valine (V) or threonine (T) at amino acid position 74 using AHo numbering system (amino acid position 58 using Kabat numbering system) (vii) asparagine (N) at amino acid position 94 using AHo numbering system (amino acid position 76 using Kabat numbering system) (viii) tyrosine (Y) or serine (S) at amino acid position 101 using AHo numbering system (amino acid position 83 using Kabat numbering system) and (ix) leucine (L) or alanine (A) at amino acid position 103 using AHo numbering (amino acid position 85 using Kabat numbering).
