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Structural analysis of the bipartite DNA-binding domain of Tc3 transposase bound to transposon DNA.

ABSTRACT: The bipartite DNA-binding domain of Tc3 transposase, Tc3A, was crystallized in complex with its transposon recognition sequence. In the structure the two DNA-binding domains form structurally related helix-turn-helix (HTH) motifs. They both bind to the major groove on a single DNA oligomer, separated by a linker that interacts closely with the minor groove. The structure resembles that of the transcription factor Pax6 DNA-binding domain, but the relative orientation of the HTH-domain is different. The DNA conformation is distorted, characterized by local narrowing of the minor groove and bends at both ends. The protein-DNA recognition takes place through base and backbone contacts, as well as shape-recognition of the distortions in the DNA. Charged interactions are primarily found in the N-terminal domain and the linker indicating that these may form the initial contact area. Two independent dimer interfaces could be relevant for bringing together transposon ends and for binding to a direct repeat site in the transposon end. In contrast to the Tn5 synaptic complex, the two Tc3A DNA-binding domains bind to a single Tc3 transposon end.

SUBMITTER: Watkins S

PROVIDER: S-EPMC514390 | biostudies-literature | 2004

REPOSITORIES: biostudies-literature

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Structural analysis of the bipartite DNA-binding domain of Tc3 transposase bound to transposon DNA.

Watkins Stephan S van Pouderoyen Gertie G Sixma Titia K TK

Nucleic acids research 20040810 14

The bipartite DNA-binding domain of Tc3 transposase, Tc3A, was crystallized in complex with its transposon recognition sequence. In the structure the two DNA-binding domains form structurally related helix-turn-helix (HTH) motifs. They both bind to the major groove on a single DNA oligomer, separated by a linker that interacts closely with the minor groove. The structure resembles that of the transcription factor Pax6 DNA-binding domain, but the relative orientation of the HTH-domain is differen ...[more]

PMID: 15304566

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Project description:The REB1 gene encodes a DNA-binding protein (Reb1p) that is essential for growth of the yeast Saccharomyces cerevisiae. Reb1p binds to sites within transcriptional control regions of genes transcribed by either RNA polymerase I or RNA polymerase II. The sequence of REB1 predicts a protein of 809 amino acids. To define the DNA-binding domain of Reb1p, a series of 5' and 3' deletions within the coding region was constructed in a bacterial expression vector. Analysis of the truncated Reb1p proteins revealed that nearly 400 amino acids of the C-terminal portion of the protein are required for maximal DNA-binding activity. To further define the important structural features of Reb1p, the REB1 homolog from a related yeast, Kluyveromyces lactis, was cloned by genetic complementation. The K. lactis REB1 gene supports active growth of an S. cerevisiae strain whose REB1 gene has been deleted. The Reb1p proteins of the two organisms generate almost identical footprints on DNA, yet the K. lactis REB1 gene encodes a polypeptide of only 595 amino acids. Comparison of the two Reb1p sequences revealed that within the region necessary for the binding of Reb1p to DNA were two long regions of nearly perfect identity, separated in the S. cerevisiae Reb1p by nearly 150 amino acids but in the K. lactis Reb1p by only 40 amino acids. The first includes a 105-amino-acid region related to the DNA-binding domain of the myb oncoprotein; the second bears a faint resemblance to myb. The hypothesis that the DNA-binding domain of Reb1p is formed from these two conserved regions was confirmed by deletion of as many as 90 amino acids between them, with little effect on the DNA-binding ability of the resultant protein. We suggest that the DNA-binding domain of Reb1p is made up of two myb-like regions that, unlike myb itself, are separated by as many as 150 amino acids. Since Reb1p protects only 15 to 20 nucleotides in a chemical or enzymatic footprint assay, the protein must fold such that the two components of the binding site are adjacent.

Project description:BackgroundWith increasing numbers of crystal structures of proteinratioDNA and proteinratioproteinratioDNA complexes publically available, it is now possible to extract sufficient structural, physical-chemical and thermodynamic parameters to make general observations and predictions about their interactions. In particular, the properties of macromolecular assemblies of multiple proteins bound to DNA have not previously been investigated in detail.Methodology/principal findingsWe have performed computational structural analyses on macromolecular assemblies of multiple proteins bound to DNA using a variety of different computational tools: PISA; PROMOTIF; X3DNA; ReadOut; DDNA and DCOMPLEX. Additionally, we have developed and employed an algorithm for approximate collision detection and overlapping volume estimation of two macromolecules. An implementation of this algorithm is available at http://promoterplot.fmi.ch/Collision1/. The results obtained are compared with structural, physical-chemical and thermodynamic parameters from proteinratioprotein and single proteinratioDNA complexes. Many of interface properties of multiple proteinratioDNA complexes were found to be very similar to those observed in binary proteinratioDNA and proteinratioprotein complexes. However, the conformational change of the DNA upon protein binding is significantly higher when multiple proteins bind to it than is observed when single proteins bind. The water mediated contacts are less important (found in less quantity) between the interfaces of components in ternary (proteinratioproteinratioDNA) complexes than in those of binary complexes (proteinratioprotein and proteinratioDNA).The thermodynamic stability of ternary complexes is also higher than in the binary interactions. Greater specificity and affinity of multiple proteins binding to DNA in comparison with binary protein-DNA interactions were observed. However, protein-protein binding affinities are stronger in complexes without the presence of DNA.Conclusions/significanceOur results indicate that the interface properties: interface area; number of interface residues/atoms and hydrogen bonds; and the distribution of interface residues, hydrogen bonds, van der Walls contacts and secondary structure motifs are independent of whether or not a protein is in a binary or ternary complex with DNA. However, changes in the shape of the DNA reduce the off-rate of the proteins which greatly enhances the stability and specificity of ternary complexes compared to binary ones.

Dataset Information

Structural analysis of the bipartite DNA-binding domain of Tc3 transposase bound to transposon DNA.

Publications

Structural analysis of the bipartite DNA-binding domain of Tc3 transposase bound to transposon DNA.

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