Relaxosome function and conjugation regulation in F-like plasmids - a structural biology perspective

• Published in: Molecular microbiology 2012-08, Vol.85 (4), p.602-617
• Main Authors: Wong, Joyce J. W., Lu, Jun, Glover, J. N. Mark
• Format: Article
• Language: English
• Subjects: Bacteria - chemistry; Bacteria - genetics; Bacterial Physiological Phenomena; Bacterial Proteins - chemistry; Bacterial Proteins - metabolism; Biological and medical sciences; Conjugation, Genetic; Crystallography; Deoxyribonucleic acid; DNA; DNA, Bacterial - genetics; DNA, Bacterial - metabolism; DNA-Binding Proteins - chemistry; DNA-Binding Proteins - metabolism; F Factor; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Bacterial; Membranes; Microbiology; Models, Biological; Plasmids; Protein Binding; Protein Conformation; Proteins; X-rays
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/j.1365-2958.2012.08131.x

Summary The tra operon of the prototypical F plasmid and its relatives enables transfer of a copy of the plasmid to other bacterial cells via the process of conjugation. Tra proteins assemble to form the transferosome, the transmembrane pore through which the DNA is transferred, and the relaxosome, a complex of DNA‐binding proteins at the origin of DNA transfer. F‐like plasmid conjugation is characterized by a high degree of plasmid specificity in the interactions of tra components, and is tightly regulated at the transcriptional, translational and post‐translational levels. Over the past decade, X‐ray crystallography of conjugative components has yielded insights into both specificity and regulatory mechanisms. Conjugation is repressed by FinO, an RNA chaperone which increases the lifetime of the small RNA, FinP. Recent work has resulted in a detailed model of FinO/FinP interactions and the discovery of a family of FinO‐like RNA chaperones. Relaxosome components include TraI, a relaxase/helicase, and TraM, which mediates signalling between the transferosome and relaxosome for transfer initiation. The structures of TraI and TraM bound to oriT DNA reveal the basis of specific recognition of DNA for their cognate plasmid. Specificity also exists in TraI and TraM interactions with the transferosome protein TraD.