Conserved features of type III secretion

Abstract

SummaryType III secretion systems (TTSSs) are essential mediators of the interaction of many Gram-negative bacteria with human, animal or plant hosts. Extensive sequence and functional similarities exist between components of TTSS from bacteria as diverse as animal and plant pathogens. Recent crystal structure determinations of TTSS proteins reveal extensive structural homologies and novel structural motifs and provide a basis on which protein interaction networks start to be drawn within the TTSSs, that are consistent with and help rationalize genetic and biochemical data. Such studies, along with electron microscopy, also established common architectural design and function among the TTSSs of plant and mammalian pathogens, as well as between the TTSS injectisome and the flagellum. Recent comparative genomic analysis, bioinformatic genome mining and genome-wide functional screening have revealed an unsuspected number of newly discovered effectors, especially in plant pathogens and uncovered a wider distribution of TTSS in pathogenic, symbiotic and commensal bacteria. Functional proteomics and analysis further reveals common themes in TTSS effector functions across phylogenetic host and pathogen boundaries. Based on advances in TTSS biology, new diagnostics, crop protection and drug development applications, as well as new cell biology research tools are beginning to emerge.

The Different Strategies Used by Salmonella to Invade Host Cells

“…They are made of an exportation apparatus, a basal body, a needle and a translocon at the tip of the needle ( Figure 3A). The structure of these T3SSs shows a high degree of conservation among pathogens (Tampakaki et al, 2004) and the Salmonella T3SS-1 apparatus shares in particular a high homology with the T3SS of Shigella, also involved in host cell invasion (Groisman & Ochman, 1993).…”

Bioinformatic and Biochemical Evidence for the Identification of the Type III Secretion System Needle Protein ofChlamydia trachomatis

“…In contrast, the type III secretion (T3S) apparatus comprises a functionally conserved multiprotein complex spanning both the bacterial inner and outer membranes and the periplasm. Hence, many of the proteins that constitute the T3S apparatus are highly conserved among species and are easily identified in protein homology searches (20,21,57).…”

Biochemical and Localization Analyses of Putative Type III Secretion Translocator Proteins CopB and CopB2 of Chlamydia trachomatis Reveal Significant Distinctions

“…Although a diverse array of chlamydial factors likely contributes to infection, secretion of antihost proteins by a nonflagellar type III secretion system (T3SS) represents an essential mechanism for virulence. T3SSs are complex machines that are expressed by an array of Gram-negative bacteria, in which they enable vectorial secretion and translocation of antihost proteins (termed effectors) into the cytosol of an infected eukaryotic cell (19,22,51). These effector proteins vary depending on the pathogen but generally act by manipulating host cellular processes to promote survival of the respective bacterium.…”