Defense Peptides From the α-Hairpinin Family Are Components of Plant Innate Immunity

Abstract

Plant immunity represents a sophisticated system, including both basal and inducible mechanisms, to prevent pathogen infection. Antimicrobial peptides (AMPs) are among the innate immunity components playing a key role in effective and rapid response against various pathogens. This review is devoted to a small family of defense peptides called α-hairpinins. The general characters of the family, as well as the individual features of each member, including biological activities, structures of precursor proteins, and spatial structures, are described. Possible applications of α-hairpinin peptides in drug design are discussed.

Keywords: antimicrobial peptides; defense peptides; plant innate immunity; primary and spatial structures; protein-precursors; α-hairpinins.

FIGURE 1

Amino acid sequence alignment of α-hairpinin peptides. Following peptides sequences are shown in alignment: MBP-1 from Zea mays (P28794); EcAMP1 from Echinochloa crus-galli (P86698); Tk-AMP-X1 (CCP19155.1); Sm-AMP-X (C0HJD6); Luffin P1 from Luffa aegyptiaca (P56568); VhTI from Veronica hederifolia (P85981); BWI-2b, and BWI-2c from Fagopyrum esculentum (no accession number and P86794); C2 peptide from Cucurbita maxima (Q9ZWI3). The cysteine residues are shown in gray; disulfide bridges shown in black lines above; the functional for trypsin inhibitors Arg residues are boxed.

FIGURE 2

3D structures of α-hairpinins: BWI-2c (PDB code 2LQX), VhTI (PDB code 2PLX), EcAMP1 (PDB code 2L2R), Luffin P1 (PDB code 2L37), Tk-AMP-X2 (PDB code 2M6A). Disulfide bridges are shown as yellow sticks and the corresponding cysteine residue numbers are specified, crucial for trypsin inhibitors Arg residues are shown in red and specified.

FIGURE 3

Two types of α-hairpinin precursors. The first type of precursors had C-terminal domain with similarity to vicilin seed storage peptide, while those of the second type shown no similarity. Signal peptides (SP) and C-terminal domains are boxed; HD – hydrophobic domain. Mature α-hairpinins with biological activity are shown as gray boxes and indicated in bold.