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Function of Pro‐185 in the ProCys of conserved motif IV in the Eco RII [cytosine‐C5]‐DNA methyltransferase
Author(s) -
Kossykh Valeri G.,
Schlagman Samuel L.,
Hattman Stanley
Publication year - 1995
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(95)00795-b
Subject(s) - cytosine , methyltransferase , dna , chemistry , stereochemistry , residue (chemistry) , biochemistry , dna methyltransferase , methylation
ProCys in the conserved sequence motif IV of [cytosine‐C5]‐DNA methyltransferases is known to be part of the catalytic site. The Cys residue is directly involved in forming a covalent bond with the C6 of the target cytosine. We have found that substitution of Pro‐185 with either Ala or Ser resulted in a reduced rate of methyl group transfer by the Eco RII DNA methyltransferase. In addition, we observed an increase in the K m for substrate (AdoMet), but a decrease in the K m for substrate DNA. This is reflected in minor changes in k cat / K m for DNA, but in 10‐ to 100‐fold reductions in k cat / K m for AdoMet. This suggests that Pro‐185 is important to properly orient the activated cytosine and AdoMet for methyl group transfer by direct interaction with AdoMet and indirectly via the Cys interaction with cytosine.