PROSITE documentation PDOC00619

Barwin domain signatures and profile

Barwin [1] is a barley seed protein of 125 residues that binds weakly a chitin analog. It contains six cysteines involved in disulfide bonds, as shown in the following schematic representation.

                              +---------------+
                              |    *****      |                ****
    xxxxxxxxxxxxxxxCxxxxxxxxxxCxxxxCxCxxxxxxxxCxxxxxxxxxxxxxxxxxxCx
                   |               | |                           |
                   +---------------+ +---------------------------+

'C': conserved cysteine involved in a disulfide bond.
'*': position of the patterns.

Barwin is closely related to the following proteins:

• Hevein, a wound-induced protein found in the latex of rubber trees.
• HEL, an Arabidopsis thaliana hevein-like protein [2].
• Win1 and win2, two wound-induced proteins from potato.
• Pathogenesis-related protein 4 from tobacco.

Hevein and the win1/2 proteins consist of an N-terminal chitin-binding domain followed by a barwin-like C-terminal domain of ~122 residues. Barwin and its related proteins could be involved in a defense mechanism in plants [1].

The dominating structural feature of the barwin domain is a well-defined four-stranded antiparallel β-sheet, two parallel β-sheets packed antiparallel to each other and four short α-helices (see <PDB:1BW3>) [3].

As signature patterns, we selected two highly conserved regions that contain some of the cysteines. We also developed a profile that covers the entire barwin domain.