Role of protein prenyltransferases in modifying effectors from infectious bacterium (739.7)

Abstract

Protein prenylation is an important post‐translational modification. Many G‐proteins, such as Ras and Rho, are prenylated in order to anchor them to the cell membrane. Protein farnesyltransferase (FTase) and geranylgeranyltransferase (GGTase) add 15‐carbon farnesyl groups and 20‐carbon geranylgeranyl groups to proteins, respectively. Substrate specificity for FTase and GGTase is minimally described by the Cza2X paradigm where C is a cysteine residue four amino acids from the C‐terminus, followed by two amino acids (z is variable; a2 is aliphatic) and an X group that specifies which prenyltransferase is preferred, though there is significant substrate overlap. Recent experiments have demonstrated that infectious bacterium Legionella pneumophila requires host cell farnesylation machinery to induce pulmonary disease. Ankyrin b, an essential Legionella effector protein, is farnesylated by the host FTase, which is important for evasion of the endocytic pathway and protein function. Prenylation of effector proteins may be a general method used by pathogenic bacteria to anchor proteins in hosts. To investigate the prevalence of prenylation of bacterial proteins, we have measured the reactivity of mammalian FTase and GGTase‐I both in vivo and in vitro with peptide sequences derived from proteins expressed in pathogenic bacteria. We have shown that FTase and GGTase are capable of prenylating bacterial Cza2X motifs in vitro and in vivo through peptide assays and in vivo cellular localization of GFP fusion proteins. We have also tested a series of prenyl donor analogs synthesized in the Gibbs laboratory with FTase and GGTase to identify analogs with similar substrate specificity to in vivo prenyl donors to use as tools for defining the prenylome. These studies will further our understanding of the many ways protein prenyltransferases regulate cellular processes and how inhibition of these enzymes may be incorporated into treatment of bacterial infections and other diseases.Grant Funding Source: Supported by NIH F31 Diversity Fellowship