The FtsK-like motor TraB is a DNA-dependent ATPase that forms higher-order assemblies

• Published in: The Journal of biological chemistry Vol. 294; no. 13; pp. 5050 - 5059
• Main Authors: Amado, Eric, Muth, Günther, Arechaga, Ignacio, Cabezón, Elena
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 29-03-2019; American Society for Biochemistry and Molecular Biology
• Subjects: Adenosine Triphosphatases - chemistry; Adenosine Triphosphatases - metabolism; antibiotics; ATPase; bacterial conjugation; Bacterial Proteins - chemistry; Bacterial Proteins - metabolism; conjugal plasmid transfer; DNA binding protein; DNA segregation; DNA translocase; DNA translocation; DNA, Bacterial - chemistry; DNA, Bacterial - metabolism; DNA-dependent ATPase; FtsK-like ATPase; G-quadruplex; G-Quadruplexes; Microbiology; Models, Molecular; motor protein; Protein Binding; Protein Domains; Protein Multimerization; Streptomyces; Streptomyces - chemistry; Streptomyces - metabolism; TRS sequence; bacterial conjugation; motor protein; ATPase; DNA binding protein; G-quadruplex; Streptomyces; FtsK-like ATPase; DNA translocation; DNA translocase; DNA segregation; DNA-dependent ATPase; TRS sequence; conjugal plasmid transfer; antibiotics
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.RA119.007459

TraB is an FtsK-like DNA translocase responsible for conjugative plasmid transfer in mycelial Streptomyces. Unlike other conjugative systems, which depend on a type IV secretion system, Streptomyces requires only TraB protein to transfer the plasmid as dsDNA. The γ-domain of this protein specifically binds to repeated 8-bp motifs on the plasmid sequence, following a mechanism that is reminiscent of the FtsK/SpoIIIE chromosome segregation system. In this work, we purified and characterized the enzymatic activity of TraB, revealing that it is a DNA-dependent ATPase that is highly stimulated by dsDNA substrates. Interestingly, we found that unlike the SpoIIIE protein, the γ-domain of TraB does not confer sequence-specific ATPase stimulation. We also found that TraB binds G-quadruplex DNA structures with higher affinity than TraB-recognition sequences (TRSs). An EM-based structural analysis revealed that TraB tends to assemble as large complexes comprising four TraB hexamers, which might be a prerequisite for DNA translocation across cell membranes. In summary, our findings shed light on the molecular mechanism used by the DNA-translocating motor TraB, which may be shared by other membrane-associated machineries involved in DNA binding and translocation.