R. Roskoski et P. Ritchie, ROLE OF THE CARBOXYTERMINAL RESIDUE IN PEPTIDE BINDING TO PROTEIN FARNESYLTRANSFERASE AND PROTEIN GERANYLGERANYLTRANSFERASE, Archives of biochemistry and biophysics (Print), 356(2), 1998, pp. 167-176
Protein farnesyltransferase and protein geranylgeranyltransferase-I ca
talyze the prenylation of a cysteinyl group located four residues upst
ream of the carboxyl terminus. The identity of the carboxyterminal res
idue plays a significant role in determining the ability of compounds
to bind to each enzyme and to serve as substrate. We compared the bind
ing and substrate specificities of peptides with carboxyterminal subst
itutions to determine which residues promote selectivity and which res
idues promote recognition by both enzymes. Using tetrapeptide inhibito
rs with the general structure L-penicillamine-valine-isoleucine-X and
substrates with the structure Lys-Lys-Ser-Ser-Cys-Val-Ile-X, we measur
ed their respective K-i, K-m, and k(cat) values for both recombinant r
at protein farnesyltransferase and recombinant rat protein geranylgera
nyltransferase-I. We studied the roles of carboxyterminal branched res
idues (leucine, isoleucine, valine, and penicillamine) and linear resi
dues (methionine, cysteine, homocysteine, alanine, aminobutyrate, and
aminohexanoate) in promoting interaction with the enzymes. For protein
geranylgeranyltransferase-I, peptide substrates with carboxyterminal
branched or linear residues had K-m values that were 5- to 15-fold gre
ater than the K-i values of the corresponding peptide inhibitors. For
protein farnesyltransferase, peptide substrates with carboxyterminal b
ranched residues, proline, or homoserine had K-m values that were 7- t
o 200-fold greater than the K-i values of the corresponding peptide in
hibitors. For protein farnesyltransferase the K-m and K-i values for p
eptides ending with linear residues were in general agreement, Our stu
dies indicate that the substrate and inhibitor binding specificities o
f protein geranylgeranyltransferase was much more restricted than thos
e of protein farnesyltransferase. (C) 1998 Academic Press.