There is provided a Bronstinan
protein variant comprising X1 X2 KCKX6 X7 YX9 NYPX13 X14 KCX17 X18 AX20 QCNYDCKLDKHARX34 GECFYDEX42 RNX45X46 CX48 CDYCX53YX55 (SEQ ID NO: 1) wherein X1, X20 and X47 are each independently an
amino acid having a polar uncharged
side chain, X2 is an
amino acid having a negatively charged
side chain, X6 is
glutamine (E) or an
amino acid having a positively charged
side chain, X7, X13, X18, X45 and X48 are each independently an amino acid having a hydrophobic side chain, X7, X13, X18, X45 and X48 are each independently an amino acid having a hydrophobic side chain, X7, X13, X18 X17 is
lysine (K) or an amino acid having a polar uncharged side chain, X14 is
arginine (R) or an amino acid having a polar uncharged side chain, X9 is
arginine (R) or an amino acid having a negatively charged side chain, X42 is an amino acid having a positively charged side chain, X34 is
alanine or an amino acid having a polar uncharged side chain, X17 is
lysine (K) or an amino acid having a polar uncharged side chain, X14 is
arginine (R) or an amino acid having a polar uncharged side chain. X46 is an amino acid having a polar uncharged side chain, X53 is
glutamic acid,
glutamine or
lysine, and X55 is
proline, arginine,
threonine or no residue. Also disclosed are polynucleotides encoding the bristinin variants, cells expressing the bristinin variants, and methods of making the bristinin variants.