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KP4 fungal toxin inhibits growth in Ustilago maydis by blocking calcium uptake
Author(s) -
Gage Matthew J.,
Bruenn Jeremy,
Fischer Marc,
Sanders Dale,
Smith Thomas J.
Publication year - 2001
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2001.02554.x
Subject(s) - biology , ustilago , calcium , microbiology and biotechnology , egta , biochemistry , medicine , gene
KP4 is a virally encoded fungal toxin secreted by the P4 killer strain of Ustilago maydis . From our previous structural studies, it seemed unlikely that KP4 acts by forming channels in the target cell membrane. Instead, KP4 was proposed to act by blocking fungal calcium channels, as KP4 was shown to inhibit voltage‐gated calcium channels in rat neuronal cells, and its effects on fungal cells were abrogated by exogenously added calcium. Here, we extend these studies and demonstrate that KP4 acts in a reversible manner on the cell membrane and does not kill the cells, but rather inhibits cell division. This action is mimicked by EGTA and is abrogated specifically by low concentrations of calcium or non‐specifically by high ionic strength buffers. We also demonstrate that KP4 affects 45 Ca uptake in U. maydis . Finally, we show that cAMP and a cAMP analogue, N 6,2′‐O‐dibutyryladenosine 3′:5′‐cyclic monophosphate, both abrogate KP4 effects. These results suggest that KP4 may inhibit cell growth and division by blocking calcium‐regulated signal transduction pathways.