Construction of phosphatidylethanolamine-less strain of Saccharomyces cerevisiae. Effect on amino acid transport

A triple yeast mutant was constructed which lacks BST1, the gene for sphing osine lyase, besides the phosphatidylserine decarboxylases PSD1 and PSD2. I n this yeast mutant, which can only be grown in the presence of exogenous e thanolamine, phosphatidylethanolamine can be depleted to very low levels. U nder those conditions, respiration as well as glucose and 3-O-methylglucose uptake proceed unaffected. Plasma membrane ATPase is as active in these ce lls as that of control cells grown in the presence of ethanolamine. Drastic ally decreased, however, are H+/amino acid symporters. The activities of ar ginine (Can1p), proline (Put4p) and general amino acid permease (Gap1p) are decreased more than 20-fold. Amino acid transport in yeast is dependent on coupling to the proton motive force. It can be envisaged that phosphatidyl ethanolamine might play a role in this process or in the early steps of the secretion pathway common for all amino acid permeases or, eventually, it c ould affect the transport proteins directly at the plasma membrane. Transfo rmation of the triple mutant with a CEN plasmid harbouring BST1 wild-type g ene totally reversed its phenotype to that observed in the double mutant, C opyright (C) 2000 John Wiley & Sons, Ltd.