Activity, delivery, and diversity of Type VI secretion effectors

• Published in: Molecular microbiology Vol. 115; no. 3; pp. 383 - 394
• Main Authors: Jurėnas, Dukas, Journet, Laure
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01.03.2021; Wiley
• Subjects: Antiinfectives and antibacterials; bacterial competition; bacterial toxins; Biochemistry, Molecular Biology; Cell division; Conserved sequence; Contractility; Cytoplasm; Deoxyribonucleic acid; DNA; Domains; Effectors; Energy resources; Energy sources; Life Sciences; Lysis; Prey; protein secretion; Proteins; Secretion; T6SS; Toxins; effectors; bacterial toxins; T6SS; bacterial competition; protein secretion
• ISSN: 0950-382X; 1365-2958; 1365-2958
• DOI: 10.1111/mmi.14648

The bacterial type VI secretion system (T6SS) system is a contractile secretion apparatus that delivers proteins to neighboring bacterial or eukaryotic cells. Antibacterial effectors are mostly toxins that inhibit the growth of other species and help to dominate the niche. A broad variety of these toxins cause cell lysis of the prey cell by disrupting the cell envelope. Other effectors are delivered into the cytoplasm where they affect DNA integrity, cell division or exhaust energy resources. The modular nature of T6SS machinery allows different means of recruitment of toxic effectors to secreted inner tube and spike components that act as carriers. Toxic effectors can be translationally fused to the secreted components or interact with them through specialized structural domains. These interactions can also be assisted by dedicated chaperone proteins. Moreover, conserved sequence motifs in effector‐associated domains are subject to genetic rearrangements and therefore engage in the diversification of the arsenal of toxic effectors. This review discusses the diversity of T6SS secreted toxins and presents current knowledge about their loading on the T6SS machinery. The type VI secretion system (T6SS) is a widespread bacterial weapon that delivers toxic effectors into target cells. The T6SS effector repertoire continues to be uncovered and we focus in this review on effectors with antibacterial activities, highlighting their diverse biochemical activities and cellular targets. Considering the recent advances in the field, we then discuss how these antibacterial toxins are selected and loaded onto the machinery for delivery.