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Mol. Cell. Biol., 04 1997, 1986-1994, Vol 17, No. 4
S Yalovsky, CE Trueblood, KL Callan, JO Narita, SM Jenkins, J Rine and W Gruissem
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.
Copyright © 1997, American Society for Microbiology
Plant farnesyltransferase can restore yeast Ras signaling and mating
Department of Plant and Microbial Biology, University of California, Berkeley 94720, USA.
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