PROLIFERATION OF INTRACELLULAR MEMBRANE STRUCTURES UPON HOMOLOGOUS OVERPRODUCTION OF CYTOCHROME-P-450 IN CANDIDA-MALTOSA

In an alkane-assimilating yeast, Candida maltosa, a cultivation on alk ane causes both induction of endoplasmic reticulum (ER)-resident membr ane proteins, such as cytochrome P-450, and proliferation of ER. In th is study, individual genes for alkane-inducible forms of cytochrome P- 450 (P-450alk) were homologously overexpressed in C. maltosa using a g alactose-inducible expression system developed in this yeast. Immunoel ectron microscopy revealed that, upon the overexpression, a dramatic p roliferation of ER occurred, in which overproduced P-450alk protein ac cumulated. The proliferated membranes were mainly tubular forms and st acks of paired membranes were also observed after prolonged expression . The tubular forms were morphologically very similar to the prolifera ted ER in alkane-induced C. maltosa cells. The observed proliferation of ER membranes by homologous overproduction of P-450alk, here depicte d, will provide a unique opportunity for investigating the mechanisms by which cells regulate ER biogenesis, in comparison with the intrinsi c form of ER proliferation.