title: Chemically prepared hevein domains: effect of C-terminal truncation and the mutagenesis of aromatic residues on the affinity for chitin.
abstract: Chemically prepared hevein domains (HDs), N-terminal domain of an antifungal protein from Nicotiana tabacum (CBP20-N) and an antimicrobial peptide from Amaranthus caudatus (Ac-AMP2), were examined for their affinity for chitin, a beta-1,4-linked polymer of N-acetylglucosamine. An intact binding domain, CBP20-N, showed a higher affinity than a C-terminal truncated domain, Ac-AMP2. The formation of a pyroglutamate residue from N-terminal Gln of CBP20-N increased the affinity. The single replacement of any aromatic residue of Ac-AMP2 with Ala resulted in a significant reduction in affinity, suggesting the importance of the complete set of three aromatic residues in the ligand binding site. The mutations of Phe18 of Ac-AMP2 to the residues with larger aromatic rings, i.e. Trp, beta-(1-naphthyl)alanine or beta-(2-naphthyl)alanine, enhanced the affinity, whereas the mutation of Tyr20 to Trp reduced the affinity. The affinity of an HD for chitin might be improved by adjusting the size and substituent group of stacking aromatic rings.
authors.affiliation: Biomolecules Department, National Institute of Bioscience and Human Technology, 1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan. muraki@nibh.go.jp
authors.forename: M
authors.initials: M
authors.lastname: Muraki
authors.forename: H
authors.initials: H
authors.lastname: Morii
authors.forename: K
authors.initials: K
authors.lastname: Harata
mesh_terms: D019943:Amino Acid Substitution; D023181:Antimicrobial Cationic Peptides; D002686:Chitin / Q000737:chemistry*; D037102:Lectins / Q000737:chemistry*; D019684:Magnoliopsida / Q000737:chemistry; D008958:Models, Molecular; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000737:chemistry*; D010649:Phenylalanine / Q000737:chemistry; D037121:Plant Lectins; D010940:Plant Proteins / Q000737:chemistry*; D010947:Plants, Toxic; D011485:Protein Binding; D017434:Protein Structure, Tertiary / Q000502:physiology; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship; D014026:Nicotiana; D014364:Tryptophan / Q000737:chemistry; D014443:Tyrosine / Q000737:chemistry
chemical_list: D023181:Antimicrobial Cationic Peptides; D037102:Lectins; D010446:Peptide Fragments; D037121:Plant Lectins; D010940:Plant Proteins; C045875:hevein; D002686:Chitin; D014443:Tyrosine; D010649:Phenylalanine; D014364:Tryptophan