EVIDENCE FOR A FUNCTIONAL P-TYPE H-ATPASE AT THE ROUGH ENDOPLASMIC-RETICULUM OF BRYONIA-DIOICA JACQ. TENDRILS()

A catalytically active, vanadate-sensitive P-type ATPase with enzymati c, inhibitor and immunological properties similar to the plasmalemma e nzyme is associated with the rough, but not smooth, endoplasmic reticu lum obtained from tendril tissue of Bryonia dioica Jacq. using a densi ty shift discontinuous two-step gradient purification procedure. The e nzyme is present in this fraction in similar abundance as in the plasm alemma and constitutes approximately 32% of the total vanadate-sensiti ve ATPase activity of the microsomal fraction. ATP-dependent proton pu mping activity was shown for this membrane using the fluorescent dye 9 -amino-6-chloro-2-methoxyacridine. Proton potentials may be of relevan ce for rough endoplasmic reticulum functions, at least in tendrils.