Five Mechanisms of Manipulation by Bacterial Effectors: A Ubiquitous Theme

Ubiquitin, a highly conserved polypeptide of 76 amino acids, participates in a vast range of eukaryotic cell processes through its role as a reversible post-translational modifier (see review [1], Figure 1A). Such extensive utilization of a single protein within a host cell lends itself to be an ideal target for microbial manipulation. Host-pathogen co-evolution has endowed present-day pathogens with an ever-expanding repertoire of proteins that function to modulate this system. The majority of these proteins are effectors of type III secretion (T3S) or type IV secretion (T4S) pathways, which are major virulence determinants of many Gram-negative pathogens [2], [3]. This review is focused on five distinct mechanisms in which secreted bacterial effector proteins exploit the host ubiquitylation system (Figure 2). Figure 1 The three classes of host enzymes (E1, purple; E2, red; E3, yellow) involved in ubiquitin modification of target host proteins. Figure 2 Five distinct mechanisms in which bacterial proteins manipulate the host ubiquitin system.