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1.C.45 The Plant Defensin (Plant Defensin) Family

Plant defensins form ion channels capable of transporting H+, Ca2+ and K+. However a concentration as great as 10x above the toxic concentration may be required to demonstrate increased permeability. The mature peptides are about 45-54aas in length. They possess eight disulfide linked cysteines. They were initially called γ-thionins, but x-ray analyses revealed that thionins and plant defensins are structurally unrelated. Defensins are typified by a triple stranded antiparallel β-sheet plus one α-helix. The two cysteines in the CXXXC segment of the α-helix are connected to the two cysteines in the CXC segment of the C-terminal β-strand. They resemble insect defensins in fold except for the amino terminal β-strand of the plant defensins. The conserved residues include the 8 Cs, 2 Gs (at positions 13 and 34), an aromatic residue (at position 11), and an E (at position 29). Multiple plant defensin genes are found in a single plant genome.

The generalized transport reaction catalyzed by plant defensins is:

small molecules (in) ⇌ small molecules (out)

This family belongs to the: Defensin Superfamily.

References associated with 1.C.45 family:

Broekaert, W.F., B.P.A. Cammue, M.F.C. De Bolle, K. Thevissen, G.W. De Samblanx and R.W. Osborn (1997). Antimicrobial peptides from plants. Crit. Rev. Plant. Sci. 16: 297-323.
Finkina, E.I., E.I. Shramova, A.A. Tagaev, and T.V. Ovchinnikova. (2008). A novel defensin from the lentil Lens culinaris seeds. Biochem. Biophys. Res. Commun. 371: 860-865. 18468512
Garcia-Olmedo, F., A. Molina, J.M. Alamillo and P. Rodriguez-Palenzuela (1998). Plant defense peptides. Biopolymers. 479-491. 10333739