Protein argonaute

UniProtKB accession:  Q58717

Grouped By:  Matching UniProtKB accession

UniProtKB description:  A DNA-guided ssDNA endonuclease that may play a role in defense against invading genetic elements. Uses short ssDNA sequences as guides (gDNA) to bind complementary target strands, resulting in slicing of the target DNA (tDNA) (PubMed:24442234, PubMed:27741323, PubMed:28319081, PubMed:28319084). Endonucleolytically cleaves tDNA (the gDNA indicates where to cleave); two major and two minor products are seen which correspond to cleavage sites between nucleotides 9/10, 10/11, 13/14, and 14/15 downstream of the target residue base-paired with the 5'-end of the gDNA (PubMed:24442234, PubMed:27741323, PubMed:28319081, PubMed:28319084). Efficient guide-dependent tDNA cleavage requires a minimal length of 15 bp and is maximal at 19 bp (PubMed:28319081). Prefers gDNA with 5'-phosphorylated purines and 3'-pyrimidines; changing these bases alters the cleavage activity and patterns (PubMed:28319084). Also has guide-independent activity on tDNA called 'chopping' (PubMed:28319081). Probably a first round of guide-independent activity on an invading plasmid or virus would generate guide DNAs for subsequent, more efficient, guide-dependent degradation of invading nucleic acids (PubMed:28319081). Has no activity on substrate with a mismatch at positions 10 and 11, on ssDNA or RNA, nor on DNA:RNA hybrids (PubMed:24442234). Digests longer (750 bp) dsDNA as well as circular plasmid and naked genomic DNA, but not chromatin, in a guide DNA-independent manner (PubMed:28319081). Addition of endogenous histone A3 protects DNA from cleavage, while cleavage is insensitive to methylation (PubMed:28319081). When plasmid encoding active or mutated protein (Ala-541) is transformed into Sulfolobus acidocaldarius about 25-fold fewer transformants are found with active protein; reduced levels of plasmid are found in wild-type transformed cells. While S.acidocaldarius grows at a similar temperature to M.jannaschii (70 to 80 degrees Celsius) it has very different histone-like proteins, which presumably do not protect against MjAgo (PubMed:28319081). Binds ssDNA, dsDNA and DNA-RNA hybrids; binding is most efficient with dsDNA (PubMed:24442234).