KP6 is an anti-fungal protein produced by a double-stranded RNA virus. It is a neutral protein lethal to sensitive cells of the same or related species. KP6 is composed of two subunits: KP6alpha and KP6beta, which are produced after cleavage from a single precursor preprotoxin. The KP6alpha subunit is responsible for targeting while the KP6beta subunit is cytotoxic. KP6alpha can recognize some cellular receptors before interaction of the complex with KP6beta, precipitating cell death. Neither subunit is homologous in either sequence or structure to any other known cytotoxic protein, however, they have highly similar structures to each other. The major difference between the two subunits is that KP6alpha contains a hydrophobic helix at the N-terminus, which plays a key role in target recognition. This model corresponds to the KP6beta subunit.
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