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Toroidal structure and DNA cleavage by the CRISPR-associated [4Fe-4S] cluster containing Cas4 nuclease SSO0001 from Sulfolobus solfataricus.

ABSTRACT: Cas4 proteins, a core protein family associated with the microbial system of adaptive immunity CRISPR, are predicted to function in the adaptation step of the CRISPR mechanism. Here we show that the Cas4 protein SSO0001 from the archaeon Sulfolobus solfataricus has metal-dependent endonuclease and 5'?3' exonuclease activities against single-stranded DNA, as well as ATP-independent DNA unwinding activity toward double-stranded DNA. The crystal structure of SSO0001 revealed a decameric toroid formed by five dimers with each protomer containing one [4Fe-4S] cluster and one Mn(2+) ion bound in the active site located inside the internal tunnel. The conserved RecB motif and four Cys residues are important for DNA binding and cleavage activities, whereas DNA unwinding depends on several residues located near the [4Fe-4S] cluster. Our results suggest that Cas4 proteins might contribute to the addition of novel CRISPR spacers through the formation of 3'-DNA overhangs and to the degradation of foreign DNA.

SUBMITTER: Lemak S

PROVIDER: S-EPMC3889865 | biostudies-literature | 2013 Nov

REPOSITORIES: biostudies-literature

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Toroidal structure and DNA cleavage by the CRISPR-associated [4Fe-4S] cluster containing Cas4 nuclease SSO0001 from Sulfolobus solfataricus.

Lemak Sofia S Beloglazova Natalia N Nocek Boguslaw B Skarina Tatiana T Flick Robert R Brown Greg G Popovic Ana A Joachimiak Andrzej A Savchenko Alexei A Yakunin Alexander F AF

Journal of the American Chemical Society 20131111 46

Cas4 proteins, a core protein family associated with the microbial system of adaptive immunity CRISPR, are predicted to function in the adaptation step of the CRISPR mechanism. Here we show that the Cas4 protein SSO0001 from the archaeon Sulfolobus solfataricus has metal-dependent endonuclease and 5'→3' exonuclease activities against single-stranded DNA, as well as ATP-independent DNA unwinding activity toward double-stranded DNA. The crystal structure of SSO0001 revealed a decameric toroid form ...[more]

PMID: 24171432

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Project description:The all-ferrous, carbene-capped Fe(4)S(4) cluster, synthesized by Deng and Holm (DH complex), has been studied with density functional theory (DFT). The geometry of the complex was optimized for several electronic configurations. The lowest energy was obtained for the broken-symmetry (BS) configuration derived from the ferromagnetic state by reversing the spin projection of one of the high spin (S(i) = 2) irons. The optimized geometry of the latter configuration contains one unique and three equivalent iron sites, which are both structurally and electronically clearly distinguishable. For example, a distinctive feature of the unique iron site is the diagonal Fe···S distance, which is 0.3 Å longer than for the equivalent irons. The calculated (57)Fe hyperfine parameters show the same 1:3 pattern as observed in the Mössbauer spectra and are in good agreement with experiment. BS analysis of the exchange interactions in the optimized geometry for the 1:3, M(S) = 4, BS configuration confirms the prediction of an earlier study that the unique site is coupled to the three equivalent ones by strong antiferromagnetic exchange (J > 0 in J ?(j<4)?(4)·?(j)) and that the latter are mutually coupled by ferromagnetic exchange (J' < 0 in J' ?(i<j<4)?(i)·?(j)). In combination, these exchange couplings stabilize an S = 4 ground state in which the composite spin of the three equivalent sites (S(123) = 6) is antiparallel to the spin (S(4) = 2) of the unique site. Thus, DFT analysis supports the idea that the unprecedented high value of the spin of the DH complex and, by analogy, of the all-ferrous cluster of the Fe-protein of nitrogenase, results from a remarkably strong dependence of the exchange interactions on cluster core geometry. The structure dependence of the exchange-coupling constants in the Fe(II)-(?(3)-S)(2)-Fe(II) moieties of the all-ferrous clusters is compared with the magneto-structural correlations observed in the data for dinuclear copper complexes. Finally, we discuss two all-ferric clusters in the light of the results for the all-ferrous cluster.

Dataset Information

Toroidal structure and DNA cleavage by the CRISPR-associated [4Fe-4S] cluster containing Cas4 nuclease SSO0001 from Sulfolobus solfataricus.

Publications

Toroidal structure and DNA cleavage by the CRISPR-associated [4Fe-4S] cluster containing Cas4 nuclease SSO0001 from Sulfolobus solfataricus.

Similar Datasets

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