Contents

Hin recombinase

Hin functions by binding to two 26bp imperfect inverted repeat sequences as a homodimer. These hin binding sites flank the invertible segment which not only encodes the Hin gene itself, but also contains an enhancer element to which the bacterial Fis proteins binds with nanomolar affinity. Four molecules of Fis bind to this site as a homodimers and are required for the recombination reaction to proceed.

The initial reaction requires binding of Hin and Fis to their respective DNA sequences and assemble into a higher-order nucleoprotein complex with branched plectonemic supercoils with the aid of the DNA bending protein HU. At this point, it is believed that the Fis protein modulates subtle contacts to activate the reaction, possibly through direct interactions with the Hin protein. Activation of the 4 catalytic serine residues within the Hin tetramer make a 2-bp double stranded DNA break and forms a covalent reaction intermediate. The DNA cleavage event also requires the divalent metal cation magnesium. A large conformational change reveals a large hydrophobic interface that allows for subunit rotation which may be driven by superhelical torsion within the protein-DNA complex. After this 180° rotation, Hin returns to its native conformation and re-ligates the cleaved DNA, without the aid of high energy cofactors and without the loss of any DNA.

References[edit]

• Dhar G, Sanders E, Johnson R (2004). "Architecture of the hin synaptic complex during recombination: the recombinase subunits translocate with the DNA strands". Cell. 119 (1): 33–45. doi:10.1016/j.cell.2004.09.010. PMID 15454079.
• Sanders E, Johnson R (2004). "Stepwise dissection of the Hin-catalyzed recombination reaction from synapsis to resolution". J Mol Biol. 340 (4): 753–66. CiteSeerX 10.1.1.501.4728. doi:10.1016/j.jmb.2004.05.027. PMID 15223318.
• Kamtekar S, Ho R, Cocco M, Li W, Wenwieser S, Boocock M, Grindley N, Steitz T (2006). "Implications of structures of synaptic tetramers of gamma delta resolvase for the mechanism of recombination". Proc Natl Acad Sci USA. 103 (28): 10642–7. Bibcode:2006PNAS..10310642K. doi:10.1073/pnas.0604062103. PMC 1483221. PMID 16807292.
• Li W, Kamtekar S, Xiong Y, Sarkis G, Grindley N, Steitz T (2005). "Structure of a synaptic gammadelta resolvase tetramer covalently linked to two cleaved DNAs". Science. 309 (5738): 1210–5. Bibcode:2005Sci...309.1210L. doi:10.1126/science.1112064. PMID 15994378. S2CID 84409916.