Relaxases

Putative membrane protein TraK
Mass / length primary structure	546 amino acids , 62,673 Da
Identifier
External IDs	UniProt : Q07713 ;

Mobilization protein MobB
other names	Protein C
Mass / length primary structure	148 amino acids , 15,933 Da
Identifier
External IDs	UniProt : P08097 ;

Multifunctional conjugation protein TraI
other names	DNA nickase TraI, transesterase TraI
	Existing structure data : PDB 1P4D , PDB 2A0I , PDB 2L8B
Mass / length primary structure	1,756 amino acids , 192,016 Da
Identifier
External IDs	UniProt : P14565 ;
Enzyme classification
EC, category	5.99.1.2

A relaxase is a single DNA transesterase - enzyme , which some prokaryotes produced. Some viruses can also contain genetic material that codes for relaxase. Relaxases enable bacteria to exchange genetic material and thus acquire skills that were not previously available.

properties

The relaxase binds nucleic acids to a specific sequence, cuts both DNA strands and, during conjugation, guides a nucleic acid strand through a tunnel into the neighboring bacterium. The missing strand is reproduced using the template of the existing strand. For example, a conferred immunity to drugs or antibiotic resistance can then be passed on by both bacteria.

structure

Well-known relaxases are tyrosine transesterases and metalloenzymes . They use a metal ion to help transfer an ester bond from the DNA phosphodiester backbone to a catalytic tyrosine side chain on the enzyme, resulting in a long-lived covalent phosphotyrosine intermediate. The first structural descriptions of Rep relaxases were made on viruses (TYLCV and AAV-5 ) in 2002. These showed compact molecules of five-stranded, antiparallel beta leaf cores with alpha-helix structures on the edge.

etymology

The relaxase nomenclature is diverse. Well-known relaxases are divided into Rep and Mob classes, depending on whether they are used for replication - that is, genetic reproduction, or for mobilization. In bacterial plasmids , mob class relaxases are named with names such as Tra I (in plasmid RP4), Vir D2 (pTi), Trw C (R388), Tra I (F plasmid), Mob B (CloDF13) or Trs K ( pGO1).

Relaxase inhibition

Reports of relaxase inhibition by small molecules mimicking intermediates in this enzymatic relaxase reaction have been known since 2007. This can prevent the spread of antibiotic resistance.

Individual evidence

↑ Aravindan Ilangovan, Christopher WM Kay, Sandro Roier, Hassane El Mkami, Enrico Salvadori, Ellen L. Zechner, Giulia Zanetti, Gabriel Waksman: Cryo-EM Structure of a Relaxase Reveals the Molecular Basis of DNA Unwinding during Bacterial Conjugation. In: Cell (2017) doi : 10.1016 / j.cell.2017.04.010 .

[1] Aravindan Ilangovan, Christopher WM Kay, Sandro Roier, Hassane El Mkami, Enrico Salvadori, Ellen L. Zechner, Giulia Zanetti, Gabriel Waksman: Cryo-EM Structure of a Relaxase Reveals the Molecular Basis of DNA Unwinding during Bacterial Conjugation. In: Cell (2017) doi : 10.1016 / j.cell.2017.04.010 .