Solution structure of the I gamma subdomain of the Mu end DNA-binding domain of phage Mu transposase
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R T Clubb1, S Schumacher, K Mizuuchi
1Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0520, USA.
Abstract:
The MuA transposase of phase Mu is a large modular protein that plays a central role in transposition. We show that the Mu end DNA-binding domain, I beta gamma, which is responsible for binding the DNA attachment sites at each end of the Mu genome, comprises two subdomains, I beta and I gamma, that are structurally autonomous and do not interact with each other in the absence of DNA. The solution structure of the I gamma subdomain has been determined by multidimensional NMR spectroscopy. The structure of I gamma comprises a four helix bundle and, despite the absence of any significant sequence identity, the topology of the first three helices is very similar to that of the homeodomain family of helix-turn-helix DNA-binding proteins. The helix-turn-helix motif of I gamma, however, differs from that of the homeodomains in so far as the loop is longer and the second helix is shorter, reminiscent of that in the POU-specific domain.
Insights
The MuA transposase
Area of Science:
- Molecular Biology
- Structural Biology
- Genetics
Background:
- MuA transposase is crucial for transposition in bacteriophage Mu.
- The Iβγ domain binds DNA attachment sites at the ends of the Mu genome.
- This domain consists of two structurally independent subdomains: Iβ and Iγ.
Purpose of the Study:
- To elucidate the structure of the Iγ subdomain of MuA transposase.
- To understand the structural relationship between Iγ and other DNA-binding domains.
Main Methods:
- Multidimensional NMR spectroscopy was used to determine the solution structure of the Iγ subdomain.
- Structural comparisons were made with known DNA-binding protein families.
Main Results:
- The Iγ subdomain adopts a four-helix bundle structure.
- Its topology resembles that of homeodomain helix-turn-helix proteins, despite lacking sequence identity.
- The helix-turn-helix motif in Iγ shows variations compared to canonical homeodomains, similar to the POU-specific domain.
Conclusions:
- The Iγ subdomain is structurally autonomous.
- Iγ shares structural similarities with homeodomains and POU-specific domains, suggesting potential functional parallels in DNA binding.