Barwin is a basic
protein with pI above 10 and molecular mass 13.7 kDa isolated from aqueous extracts of barley seed. The complete amino acid sequence of 125 residues has been determined by a combination of conventional
protein sequencing, plasma desorption mass spectrometry, and 1H nuclear magnetic resonance spectroscopy. Three
disulfide bridges have been localized as Cys31-Cys63, Cys52-Cys86, and Cys66-Cys123 both by 1H nuclear magnetic resonance spectroscopy and by plasma desorption mass spectrometry. The N-terminal residue was identified as
pyroglutamate. Barwin is closely related to a
peptide segment of 122 residues at the C-terminal region of the
proteins encoded by two
wound-induced genes in potato plants, win1 and win2, and a
protein encoded by the
hevein gene of rubber tree. In 77 sequence positions of 125 the barwin, win1, win2, and
hevein protein sequences have amino acid sequence identity, when two gaps--one of two residues allowing for the insert of Gly23 and Ala24 and one allowing for the insert of Thr97 in the barwin sequence--are introduced in the latter three. The close sequence similarity with the
proteins encoded by the
wound-induced potato and rubber tree genes and the ability of the
protein to bind saccharides suggest that barwin might belong to a group of
proteins involved in a common defense mechanism in plants.