7QNQ

Structure of the Aux2 relaxosome protein of plasmid pLS20

Summary for 7QNQ

• Entry DOI: 10.2210/pdb7qnq/pdb
• Descriptor: Auxiliary relaxosome protein, CHLORIDE ION, MAGNESIUM ION, ... (4 entities in total)
• Functional Keywords: bacterial conjugation ribbon-helix-helix domain, dna binding protein
• Biological source: Bacillus subtilis subsp. natto
• Total number of polymer chains: 8
• Total formula weight: 137531.09

Authors

Boer, D.R.,Crespo, I. (deposition date: 2021-12-22, release date: 2022-03-09, Last modification date: 2024-06-19)

Primary citation

Crespo, I.,Bernardo, N.,Cuppari, A.,Calisto, B.M.,Val-Calvo, J.,Miguel-Arribas, A.,Meijer, W.J.J.,Carpena, X.,Gil-Ortiz, F.,Malfois, M.,Boer, D.R.
Structural and biochemical characterization of the relaxosome auxiliary proteins encoded on the Bacillus subtilis plasmid pLS20.
Comput Struct Biotechnol J, 20:757-765, 2022

PubMed Abstract: Bacterial conjugation is an important route for horizontal gene transfer. The initial step in this process involves a macromolecular protein-DNA complex called the relaxosome, which in plasmids consists of the origin of transfer () and several proteins that prepare the transfer. The relaxosome protein named relaxase introduces a nick in one of the strands of the to initiate the process. Additional relaxosome proteins can exist. Recently, several relaxosome proteins encoded on the plasmid pLS20 were identified, including the relaxase, named Rel, and two auxiliary DNA-binding factors, named Aux1 and Aux2. Here, we extend this characterization in order to define their function. We present the low-resolution SAXS envelope of the Aux1 and the atomic X-ray structure of the C-terminal domain of Aux2. We also study the interactions between the auxiliary proteins and the full-length Rel, as well as its separate domains. The results show that the quaternary structure of the auxiliary protein Aux1 involves a tetramer, as previously determined. The crystal structure of the C-terminal domain of Aux2 shows that it forms a tetramer and suggests that it is an analog of TraM of plasmid F. This is the first evidence of the existence of a TraM analog in gram positive conjugative systems, although, unlike other TraM analogs, Aux2 does not interact with the relaxase. Aux1 interacts with the C-terminal domain, but not the N-terminal domain, of the relaxase Rel. Thus, the pLS20 relaxosome exhibits some unique features despite the apparent similarity to some well-studied G- conjugation systems.

PubMed: 35198129
DOI: 10.1016/j.csbj.2021.12.041

Experimental method

X-RAY DIFFRACTION (1.89 Å)