The Relation Between Ion Absorption and Protein Synthesis in Beet Disks

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Abstract
Disks of red beet storage tissue were incubated under aseptic conditions permitting the development of various metabolic processes commonly associated with aged disks, and the effects of chloramphenicol and puromycin on protein synthesis, on the development of invertase activity and ion absorption capacity, and on ion absorption per se were determined. Low concentrations of chloramphenicol and puromycin inhibit the development of ion absorption capacity but stimulate invertase development and protein synthesis, while higher concentrations inhibit all three processes. In contrast ion absorption itself is unaffected by puromycin, but is sensitive to quite low concentrations of chloramphenicol The D-threo and L-threo isomers of chloramphenicol have sharply contrasted effects on the development, as distinct from the utilization, of ion absorption capacity. The D isomer inhibits the development of ion absorption capacity more effectively than the L isomer which in turn inhibits absorption more effectively than the D isomer. A reappraisal is made of the hypothesis that ion absorption is directly linked with protein turnover and to account for the results a model is proposed in which D-threo-chloramphenicol is active both as an uncoupler of oxidative phosphoryalation and as an inhibitor of protein synthesis, while L-threo-chloramphenicol acts only in the former capacity and puromycin only in the latter. It is concluded that the inhibition of ion uptake by chloramphenicol cannot be attributed to a contemporaneous effect on protein synthesis. However, the results are consistent with the involvement of ATPase proteins in ion uptake.