The Serine-transposases

Other TE encode transposases which resemble serine site-specific recombinases. Their chemistry is presumably similar to that of their sequence-specific recombinase cousins.

IS607 family members encode a Tpase closely resembling serine site-specific recombinases which use serine as a nucleophile for cleavage of the DNA strand (Grindley, 2002). At present little is known about transposition of this IS family although it is thought that these elements generate circular intermediates (NDF Grindley pers. comm. cited in (Filee, et al., 2007)). Presumably the enzyme catalyses similar cleavages and strand transfers as its site-specific serine recombinase cousins using a transitory 5' phosphoserine covalent intermediate. Based on transposase structures from structural genomics studies and detailed knowledge of the general serine recombinase mechanism, (Boocock & Rice, 2013) have proposed a model for the transposition mechanism. This includes a synaptic transposase tetramer (as for classical serine recombinases). The model explains the lack of target specificity exhibited in IS607 transposition (Kersulyte, et al., 2000), behaviour which is unusual for this type of recombinase.

References :

• Boocock MR & Rice PA (2013) A proposed mechanism for IS607-family serine transposases. Mob DNA 4: 24.
• Filee J, Siguier P & Chandler M (2007) Insertion sequence diversity in archaea. Microbiol Mol Biol Rev 71: 121-157.
• Grindley NDF (2002) The movement of Tn3-like elements: transposition and cointegrate resolution. Mobile DNA II,(Craig NL, Craigie R, Gellert M & Lambowitz A, eds.), pp. 230-271. ASM press, Washington DC.
• Kersulyte D, Mukhopadhyay AK, Shirai M, Nakazawa T & Berg DE (2000) Functional organization and insertion specificity of IS607, a chimeric element of Helicobacter pylori. J Bacteriol 182: 5300-5308.