Mitochondrial Interaction withHelminthosporium maydisRace T Toxin: Blocking by Dicyclohexylcarbodiimide

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Abstract
Treatment of mitochondria isolated from Texas male sterile cytoplasm corn (T mitochondria) with high concentrations of dicyclohexylcarbodiimide (DCCD) (140 nmol DCCD mg−1 mitochondrial protein) completely and immediately inhibited T mitochondrial swelling by Helminthosporium maydis Race T toxin (HmT toxin). In order to obtain a specific interaction between DCCD and the ATPase complex T mitochondria were incubated with lower DCCD concentrations (1–5 nmol DCCD mg−1 mitochondrial protein) for up to 8 h at 4 °C. After 8 h incubation in the presence of 3.75 nmol DCCD mg−1 mitochondrial protein, toxin-induced swelling was decreased by 69%. Specificity of DCCD action upon the ATPase complex was confirmed by (1) SDS gel electrophoresis and fluorographic analyses of proteins from [14C]-DCCD-treated T mitochondria and immunoprecipitates and (2) physiological experiments showing that DCCD exerted none of its other documented effects. These data suggest that HmT toxin interacts with the ATPase complex of T mitochondria either at or near the DCCD-binding protein within the membrane sector of the complex.

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