2 DISTINCT GENES ENCODE SMALL ISOPROTEOLIPIDS AFFECTING PLASMA-MEMBRANE H-ATPASE ACTIVITY OF SACCHAROMYCES-CEREVISIAE()

A small proteolipid called PMP1 is associated with yeast plasma membra ne RC-ATPase (Navarre, C., Ghislain, M., Leterme, S., Ferroud, C., Duf our, J,-P., and Goffeau, A (1992) J. Biol. Chem. 267, 6425-6428). We h ave identified a second Saccharomyces cerevisiae plasma membrane prote olipid gene by hybridization with a PMP1 probe. The sequence of the co rresponding gene, called PMP2, is 92% identical to the PMP1 gene seque nce. PMP2 encodes a 43-amino acid polypeptide that can be extracted fr om the membrane with chloroform/methanol. The two proteolipids differ at residue 21, which is an alanine in PMP1 and a serine in PMP2. The t wo PMP genes are similarly expressed in the wild-type strain, and no m odification of the level of transcription of one PMP gene is detected in a strain deleted of the other. A regulatory function of the proteol ipids is indicated by the observation that a strain lacking both PMP g enes and no longer containing plasma membrane proteolipids displays a lower V-max of the plasma membrane H+-ATPase activity.