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Structure of McrBC without DNA binding domains (Class 1)Structure of McrBC without DNA binding domains (Class 1)
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Structural highlights
Function[MCRB_ECOLI] Recognizes N4- and C5-methylcytosine (and 5-hydroxy-methylcytosines) produced by a broad range of DNA methylases and appears to act against 5-methylcytosine preceded by a purine residue. Binds to DNA containing methylated cytosines; also binds to GTP. Isoform 33 kDa is less active than isoform 51 kDa and may play a role in regulating the activity of isoform 51 kDa by competing with it in DNA and protein binding abilities. [MCRC_ECOLI] Modifies the specificity of McrB restriction by expanding the range of modified sequences restricted. Does not bind to DNA. Publication Abstract from PubMedThe AAA+ GTPase McrB powers DNA cleavage by the endonuclease McrC. The GTPase itself is activated by McrC. The architecture of the GTPase and nuclease complex, and the mechanism of their activation remained unknown. Here, we report a 3.6 A structure of a GTPase-active and DNA-binding deficient construct of McrBC. Two hexameric rings of McrB are bridged by McrC dimer. McrC interacts asymmetrically with McrB protomers and inserts a stalk into the pore of the ring, reminiscent of the gamma subunit complexed to alpha3beta3 of F1-ATPase. Activation of the GTPase involves conformational changes of residues essential for hydrolysis. Three consecutive nucleotide-binding pockets are occupied by the GTP analogue 5'-guanylyl imidodiphosphate and the next three by GDP, which is suggestive of sequential GTP hydrolysis. Structure-based mechanism for activation of the AAA+ GTPase McrB by the endonuclease McrC.,Nirwan N, Itoh Y, Singh P, Bandyopadhyay S, Vinothkumar KR, Amunts A, Saikrishnan K Nat Commun. 2019 Jul 11;10(1):3058. doi: 10.1038/s41467-019-11084-1. PMID:31296862[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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