Abstract
This chapter discusses substrate interactions of protein prenyltransferases. The posttranslational modification of proteins by isoprenoids facilitates protein–membrane and protein–protein interactions. This modification is common in a variety of proteins. It is estimated that as much as 0.5% of mammalian brain proteins are prenylated. Among the known prenylated proteins are most of the small guanosine triphosphate (GTP)-binding proteins, the γ subunits of trimeric G proteins, and nuclear lamins. Protein prenylation is likely to affect a wide variety of cellular functions. Prenylation of proteins is catalyzed by protein prenyltransferases. In the reaction a thioether bond is formed between the sulfhydryl group of a cysteine residue, located near the carboxy terminus of the acceptor protein, and either a 15-carbon farnesyl or a 20-carbon geranylgeranyl isoprenoid. The nature of the prenyl modification is highly dependent on the specificity of the prenyltransferases. The three protein prenyltransferases isolated are (1) farnesyltransferase (FTase), (2) geranylgeranyltransferase I (GGTase I), and (3) geranylgeranyltransferase II (GGTase II).The determination of farnesyl pyrophosphate binding assay using nonisolated enzyme-[3H] farnesyl pyrophosphate complex is described in the chapter.
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