Detailed mechanism for transposition by TnpA transposase involves DNA shape rather than direct protein-DNA recognition to generate an active nucleoprotein complex.
A series of single-crystal structures determined by Barabas and colleagues provides a detailed mechanism for how the TnpA transposase from Helicobacter pylori recognizes, cleaves, and integrates the IS200/IS605 class of transposable elements. An interesting aspect of the mechanism is that the transposase recognizes the transposon through the unique fold-back structure adopted by the sequences of the DNA components, rather than through direct protein-DNA interactions. This is an example of indirect readout that is reminiscent of how four-stranded junctions are recognized by recombination proteins, but is also analogous to ribonucleoproteins, in that the DNA facilitates formation of an active nucleic acid-protein complex.
Department of Biochemistry and Molecular Biology 1870 Campus Delivery, Colorado State University, Fort Collins, CO 80523-1870 USA. shing.ho@colostate.edu
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