Functional analysis of Gln-237 mutants of HhaI methyltransferase

Mi, S., Alonso, D., Roberts, R. J. (February 1995) Functional analysis of Gln-237 mutants of HhaI methyltransferase. Nucleic Acids Res, 23 (4). pp. 620-7. ISSN 0305-1048 (Print)

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DOI: 10.1093/nar/23.4.620


When the HhaI (cytosine-5) methyltransferase (M.HhaI) binds DNA it causes the target cytosine to be flipped 180 degrees out of the helix. The space becomes occupied by two amino acids, Ser-87 and Gln-237, which enter the helix from opposite sides and form a hydrogen bond to each other. Gln-237 may be involved in specific sequence recognition since it forms three hydrogen bonds to the orphan guanosine, which is the partner of the target cytosine. We have prepared all 19 mutants of Gln-237 and tested their biochemical properties. We find that mutations of this residue greatly affect the stability of the M.HhaI-DNA complex without affecting the enzyme's specificity for the target sequence. Surprisingly, all mutants retain detectable levels of enzymatic activity.

Item Type: Paper
Uncontrolled Keywords: Base Sequence Cytosine/chemistry DNA, Bacterial/chemistry/ metabolism Glycine/chemistry Guanosine/chemistry Hydrogen Bonding Models, Molecular Molecular Sequence Data Mutagenesis, Site-Directed Nucleic Acid Conformation Protein Binding Protein Conformation Research Support, U.S. Gov't, Non-P.H.S. Research Support, U.S. Gov't, P.H.S. Serine/chemistry Site-Specific DNA Methyltransferase (Cytosine-Specific)/chemistry/genetics/ metabolism Substrate Specificity
Subjects: bioinformatics > genomics and proteomics > design > nucleic acid design
bioinformatics > genomics and proteomics > genetics & nucleic acid processing > protein structure, function, modification > protein types > methyltransferase
bioinformatics > genomics and proteomics > genetics & nucleic acid processing > DNA, RNA structure, function, modification > mutations > mutagenesis
CSHL Authors:
Communities: CSHL labs
Depositing User: Jessica Koos
Date: 25 February 1995
Date Deposited: 08 Aug 2014 19:43
Last Modified: 08 Nov 2017 15:59
PMCID: PMC306729
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