DIFFERENTIAL-EFFECTS OF POLYLYSINE ON NADH-LINKED ELECTRON-TRANSFER IN CORN ROOT PLASMA-MEMBRANE VESICLES

The effects of polylysine on the electron transfer from NADH to cytoch rome ($) under bar c and ferricyanide in corn root plasma membrane ves icles were investigated. The presence of polylysine decreased the redu ction rate of cytochrome ($) under bar c but slightly stimulated the r ate of ferricyanide reduction in a pH 7.5 medium of low ionic strength . An increase in ionic strength eliminated the effects of polylysine o n ferricyanide reduction but not the inhibition of cytochrome ($) unde r bar c reduction. Kinetic analyses indicated that in high ionic stren gth medium, polylysine inhibition appeared to assume a competitive mod el suggesting its binding to cytochrome ($) under bar c reduction site . In low ionic strength medium, a complex inhibition was observed. A s tudy on the inhibitory efficiency of different size polylysines sugges ted that the reduction site of cytochrome ($) under bar c may best fit a polylysine with molecular weight close to 25,000. The results suppo rt the notion that the electron transfer from NADH to these two accept ers may involve two separated enzymes or two different sites along an electron transfer chain in the plasma membrane.