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| ==About==
| | {{Complex placeholder}} |
| '''Description''' (originally from EcoCyc<ref name='LIB:EcoCyc11.1'/>) <I>Eco</I>KI restriction-modification system
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| '''Comments''' (originally from EcoCyc<ref name='LIB:EcoCyc11.1'/>) <I>Eco</I>KI is the type IA restriction-modification enzyme complex responsible
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| for identifying and restricting unmethylated, foreign DNA and for modifying native,
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| hemimethylated DNA by methylation for self-identification. The three proteins
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| which make up <I>Eco</I>KI-HsdR, HsdM, and HsdS-are all required for
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| restriction. There is a complex that can form-HsdM2HsdS1-with only
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| methyltransferase activity. HsdM and HsdS are required for methylation.
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| HsdM contains a methyltransferase active site and a site for cofactor binding.
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| The cofactor <I>S</I>-adenosylmethionine (AdoMet) acts as the methyl donor
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| for modification. Hemimethylated DNA is preferred over unmethylated DNA as
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| substrate for modification. Interaction of HsdS with DNA requires HsdM. HsdS
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| contains two target recognition domains which recognize the sequence 5'AAC(N6)GTGC.
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| One recognizes the AAC sequence, while the other recognizes the GTGC sequence.
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| HsdR couples DNA translocation to ATP hydrolysis and contains the catalytic
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| site for restriction of the DNA. When the <I>Eco</I>KI binds its target sequence,
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| it makes another contact with the DNA which begins translocation of the DNA
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| while still remaining bound to the target sequence, creating loops. Restriction
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| occurs when translocation becomes stalled because enzymes run into each other,
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| when DNA becomes too supercoiled, when the loop of DNA between two
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| dimerized enzymes becomes taut, and when the enzyme becomes blocked,
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| such as at Holliday junctions. Endonucleolytic activity requires
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| Mg<sup>2+</sup>, ATP, and AdoMet <ref name='PMID:10839821'/><ref name='PMID:14654681'/>.
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| ==References==
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| <references/>
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| [[Category:Complexes]]
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| [[Category:E. coli complexes]]
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Add information about this complex.