Abstract
Bacteria have evolved sophisticated adaptive immune systems, called CRISPR-Cas, that provide sequence-specific protection against phage infection. In turn, phages have evolved a broad spectrum of anti-CRISPRs that suppress these immune systems. Here we report structures of anti-CRISPR protein IF9 (AcrIF9) in complex with the type I-F CRISPR RNA-guided surveillance complex (Csy). In addition to sterically blocking the hybridization of complementary dsDNA to the CRISPR RNA, our results show that AcrIF9 binding also promotes non-sequence-specific engagement with dsDNA, potentially sequestering the complex from target DNA. These findings highlight the versatility of anti-CRISPR mechanisms utilized by phages to suppress CRISPR-mediated immune systems.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
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Amino Acid Sequence
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Bacteria / genetics
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Bacteria / metabolism*
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Bacteria / virology
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Bacterial Proteins / chemistry
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Bacterial Proteins / genetics
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Bacterial Proteins / metabolism
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Bacteriophages / genetics
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Bacteriophages / metabolism*
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CRISPR-Cas Systems*
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Cryoelectron Microscopy
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DNA / chemistry
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DNA / genetics
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DNA / metabolism*
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Models, Molecular
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Multiprotein Complexes / chemistry
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Multiprotein Complexes / metabolism
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Multiprotein Complexes / ultrastructure
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Nucleic Acid Conformation
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Protein Binding
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Protein Conformation
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Proteus penneri / genetics
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Proteus penneri / metabolism
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Proteus penneri / virology
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RNA, Guide, CRISPR-Cas Systems / chemistry
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RNA, Guide, CRISPR-Cas Systems / genetics
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RNA, Guide, CRISPR-Cas Systems / metabolism*
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Sequence Homology, Amino Acid
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Viral Proteins / chemistry
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Viral Proteins / genetics
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Viral Proteins / metabolism*
Substances
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Bacterial Proteins
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Multiprotein Complexes
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RNA, Guide, CRISPR-Cas Systems
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Viral Proteins
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DNA