Nonidentical subunits of p21H-ras farnesyltransferase. Peptide binding and farnesyl pyrophosphate carrier functions.
The protein farnesyltransferase purified from rat brain contains two nonidentical subunits, alpha and beta. The holoenzyme forms a stable complex with [3H]farnesyl pyrophosphate (FPP) that can be isolated by gel filtration. The [3H]FPP is not covalently bound to the enzyme; it is released unaltered when the enzyme is denatured. When incubated with an acceptor such as p21H-ras, the complex transfers [3H]farnesyl from the bound [3H]FPP to the ras protein. This transfer is not sensitive to dilution by unbound FPP, suggesting that the [3H]FPP is bound at a site that leads to direct transfer to the p21H-ras acceptor. Cross-linking studies show that the p21H-ras binds to the lower molecular weight subunit (beta-subunit), raising the possibility that the [3H]FPP binds to the alpha-subunit. If this suggestion can be confirmed, it would invoke a reaction mechanism in which the alpha-subunit acts as a prenyl pyrophosphate carrier that delivers FPP to p21H-ras which is bound to the beta-subunit.
Reiss
Y
Y
Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas 75235.
Seabra
M C
MC
Armstrong
S A
SA
Slaughter
C A
CA
Goldstein
J L
JL
Brown
M S
MS
D019883:Alkyl and Aryl Transferases; D000595:Amino Acid Sequence; D000818:Animals; D001923:Brain Chemistry; D002846:Chromatography, Affinity; D002855:Chromatography, Thin Layer; D003432:Cross-Linking Reagents; D007700:Kinetics; D008969:Molecular Sequence Data; D010455:Peptides / Q000378:metabolism*; D011106:Polyisoprenyl Phosphates / Q000378:metabolism*; D051381:Rats; D012717:Sesquiterpenes; D013379:Substrate Specificity; D014166:Transferases / Q000378:metabolism*
D003432:Cross-Linking Reagents; D010455:Peptides; D011106:Polyisoprenyl Phosphates; D012717:Sesquiterpenes; C004808:farnesyl pyrophosphate; D014166:Transferases; D019883:Alkyl and Aryl Transferases; C064911:p21(ras) farnesyl-protein transferase