Plant farnesyltransferase can restore yeast Ras signaling and mating.
Farnesyltransferase (FTase) is a heterodimeric enzyme that modifies a group of proteins, including Ras, in mammals and yeasts. Plant FTase alpha and beta subunits were cloned from tomato and expressed in the yeast Saccharomyces cerevisiae to assess their functional conservation in farnesylating Ras and a-factor proteins, which are important for cell growth and mating. The tomato FTase beta subunit (LeFTB) alone was unable to complement the growth defect of ram1 delta mutant yeast strains in which the chromosomal FTase beta subunit gene was deleted, but coexpression of LeFTB with the plant alpha subunit gene (LeFTA) restored normal growth, Ras membrane association, and mating. LeFTB contains a novel 66-amino-acid sequence domain whose deletion reduces the efficiency of tomato FTase to restore normal growth to yeast ram1 delta strains. Coexpression of LeFTA and LeFTB in either yeast or insect cells yielded a functional enzyme that correctly farnesylated CaaX-motif-containing peptides. Despite their low degree of sequence homology, yeast and plant FTases shared similar in vivo and in vitro substrate specificities, demonstrating that this enzymatic modification of proteins with intermediates from the isoprenoid biosynthesis pathway is conserved in evolutionarily divergent eukaryotes.
Yalovsky
S
S
Department of Plant and Microbial Biology, University of California, Berkeley 94720, USA.
Trueblood
C E
CE
Callan
K L
KL
Narita
J O
JO
Jenkins
S M
SM
Rine
J
J
Gruissem
W
W
D019883:Alkyl and Aryl Transferases; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D017124:Conserved Sequence; D017931:DNA Primers / Q000235:genetics; D051231:Farnesyltranstransferase; D006801:Humans; D018551:Solanum lycopersicum / Q000201:enzymology / Q000235:genetics; D000072235:Mating Factor; D008969:Molecular Sequence Data; D009154:Mutation; D010455:Peptides / Q000378:metabolism; D011487:Protein Conformation; D051381:Rats; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014166:Transferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
D017931:DNA Primers; D010455:Peptides; D000072235:Mating Factor; D014166:Transferases; D019883:Alkyl and Aryl Transferases; D051231:Farnesyltranstransferase; D018631:ras Proteins