1j57
NuiA
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OverviewOverview
Nuclease A (NucA) from Anabaena sp. is a non-specific endonuclease able to, degrade single and double-stranded DNA and RNA. The endonucleolytic, activity is inhibited by the nuclease A inhibitor (NuiA), which binds to, NucA with 1:1 stoichiometry and picomolar affinity. In order to better, understand the mechanism of inhibition, the solution structure of NuiA was, determined by NMR methods. The fold of NuiA is an alpha-beta-alpha, sandwich but standard database searches by DALI and TOP revealed no, structural homologies. A visual inspection of alpha-beta-alpha folds in, the CATH database revealed similarities to the PR-1-like fold (SCOP, nomenclature). The similarities include the ordering of secondary, structural elements, a single helix on one face of the alpha-beta-alpha, sandwich, and three helices on the other face. However, a major difference, is in the IV helix, which in the PR-1 fold is short and perpendicular to, the I and III helices, but in NuiA is long and parallel to the I and III, helices. Additionally, a strand insertion in the beta-sheet makes the NuiA, beta-sheet completely antiparallel in organization. The fast time-scale, motions of NuiA, characterized by enhanced flexibility of the extended, loop between helices III and IV, also show similarities to P14a, which is, a PR-1 fold. We propose that the purpose of the PR-1 fold is to form a, stable scaffold to present this extended structure for biological, interactions with other proteins. This hypothesis is supported by data, that show that when NuiA is bound to NucA significant changes in chemical, shift occur in the extended loop between helices III and IV.
About this StructureAbout this Structure
1J57 is a Single protein structure of sequence from Anabaena sp.. Full crystallographic information is available from OCA.
ReferenceReference
The nuclease A inhibitor represents a new variation of the rare PR-1 fold., Kirby TW, Mueller GA, DeRose EF, Lebetkin MS, Meiss G, Pingoud A, London RE, J Mol Biol. 2002 Jul 19;320(4):771-82. PMID:12095254
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