Bacterial adaptive immunity uses CRISPR (clustered regularly interspaced short palindromic repeats)–associated (Cas) proteins together with CRISPR transcripts for foreign DNA degradation. In type II CRISPR-Cas systems, activation of Cas9 endonuclease for DNA recognition upon guide RNA binding occurs by an unknown mechanism. Crystal structures of Cas9 bound to single-guide RNA reveal a conformation distinct from both the apo and DNA-bound states, in which the 10-nucleotide RNA “seed” sequence required for initial DNA interrogation is preordered in an A-form conformation. This segment of the guide RNA is essential for Cas9 to form a DNA recognition–competent structure that is poised to engage double-stranded DNA target sequences. We construe this as convergent evolution of a “seed” mechanism reminiscent of that used by Argonaute proteins during RNA interference in eukaryotes.
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Salford Scientific Supplies Ltd
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Our staff at Salford Scientific are scientifically educated and experienced to support you post sale.
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Salford Scientific Supplies
A supplier of pre-owned and new scientific equipment to laboratories in university and industry.
All equipment is fully checked out for completeness and functionality.