Thionins

Thionins are a class of small, cysteine-rich proteins found in plants. They are characterized by their high cysteine content, typically forming three intramolecular disulfide bonds, which contributes to their compact, stable structure. Thionins are often found in seeds, leaves, and other plant tissues. Their primary role is believed to be related to plant defense.

These proteins exhibit antimicrobial activity, effective against a range of bacteria and fungi. This suggests they play a part in protecting plants from pathogen infection. Thionins can disrupt microbial cell membranes, leading to cell death. Beyond direct antimicrobial action, they may also contribute to defense by modulating plant immune responses.

The structure of thionins is well-conserved, with a common three-dimensional fold consisting of an alpha-helix and two antiparallel beta-sheets. This structural motif is crucial for their biological activity. Thionins are synthesized as larger precursor proteins, which are then processed to yield the mature, active forms. They are a diverse group, with many different thionin sequences identified across various plant species. Their study is important for understanding plant immunity and for potential applications in agriculture as natural biopesticides.