Protein Export According to Schedule: Architecture, Assembly, and Regulation of Type III Secretion Systems from Plant- and Animal-Pathogenic Bacteria

Abstract

SUMMARY Flagellar and translocation-associated type III secretion (T3S) systems are present in most Gram-negative plant- and animal-pathogenic bacteria and are often essential for bacterial motility or pathogenicity. The architectures of the complex membrane-spanning secretion apparatuses of both systems are similar, but they are associated with different extracellular appendages, including the flagellar hook and filament or the needle/pilus structures of translocation-associated T3S systems. The needle/pilus is connected to a bacterial translocon that is inserted into the host plasma membrane and mediates the transkingdom transport of bacterial effector proteins into eukaryotic cells. During the last 3 to 5 years, significant progress has been made in the characterization of membrane-associated core components and extracellular structures of T3S systems. Furthermore, transcriptional and posttranscriptional regulators that control T3S gene expression and substrate specificity have been described. Given the architecture of the T3S system, it is assumed that extracellular components of the secretion apparatus are secreted prior to effector proteins, suggesting that there is a hierarchy in T3S. The aim of this review is to summarize our current knowledge of T3S system components and associated control proteins from both plant- and animal-pathogenic bacteria.

The inner rod protein controls substrate switching and needle length in a Salmonella type III secretion system

“…These machines exert their function by delivering effector proteins into target cells with the capacity to modulate a variety of cellular processes for the benefit of the pathogens or symbionts that encode them (4). Type III secretion systems (TTSSs), comprising >20 proteins, are among the most complex protein secretion machines so far identified (5,6). Salmonella Typhimurium, a cause of gastroenteritis in humans, encodes two TTSSs within its pathogenicity islands 1 (SPI-1) and 2 (SPI-2), which are essential for pathogenicity (7,8).…”

“…TTSSs consist of the envelope-associated needle complex, which mediates the passage of the secreted proteins through the bacterial envelope, and several cytoplasmic accessory proteins, which are required for the recognition and sorting of the proteins destined to travel this pathway (5,6,9,10). The needle complex is composed of a multiring, envelope-associated base substructure, and a filament or needle seated on the base, projecting outward from the bacterial surface (9,11).…”

Pre- and Post-Processing Workflow for Affinity Purification Mass Spectrometry Data

“…The type III secretion system is a well-studied macromolecular machinery composed of at least 15 interacting structural proteins 41 (see supplemental Figure 17). The type III secretion holo-complex can be subdivided into three parts:…”

In silico Determination of Efficiency of Plant Secondary Metabolites to Eradicate Trachoma- A Blinding Keratoconjuctivitis Disease

“…T3SS is composed of several structural proteins, forms the secretion needle which act like molecular syringe to pass the antihost bacterial "effector" proteins (Betts-Hampikian and Fields, 2010). T3SS assembly, structure, function and its regulation are exclusively reviewed by Deng et al (2017). T3SS is said to contain three cellular membranes, the bacterial inner membrane, the outer membrane and eukaryotic host cell membrane (Deng et al, 2017).…”

“…T3SS assembly, structure, function and its regulation are exclusively reviewed by Deng et al (2017). T3SS is said to contain three cellular membranes, the bacterial inner membrane, the outer membrane and eukaryotic host cell membrane (Deng et al, 2017). The general function of T3SS includes host immune responses, cytoskeletal dynamics, vesicle transport and signal transduction pathways (Buttner, 2012).…”