TnpR

tnpR is a gene found in bacterial transposons of the Tn3 family. It encodes the TnpR resolvase, a site-specific recombinase that promotes the resolution of cointegrates formed during replicative transposition. The gene is typically located adjacent to tnpA, which encodes the transposase.

The TnpR resolvase acts at defined res (resolution) sites within the transposon. Through a reaction characteristic of serine recombinases, TnpR catalyzes recombination between these sites, separating the cointegrate into individual donor and target molecules and enabling propagation of the transposon. In most systems, TnpR functions in conjunction with TnpA and is essential for completing the transposition cycle.

Biochemically, TnpR is a DNA-binding protein that belongs to the resolvase family of site-specific recombinases, with conserved catalytic residues and a DNA-binding domain that recognizes the res sites within the transposon. The protein operates as part of the transposition machinery to ensure accurate resolution of cointegrates and maintenance of genetic elements after transposition events.

Distribution and significance: tnpR is found in Tn3 and related transposons in various Gram-negative bacteria, often on plasmids. By enabling efficient transposition and resolution of cointegrates, tnpR contributes to horizontal gene transfer and the dissemination of genetic traits carried by transposons, including antibiotic resistance determinants in some contexts.