C Katsuda

M Ikehara

S Kanaya

S Kimura

The role of the three cysteine residues at positions 13, 63 and 133 in Escherichia coli RNAase H, an enzyme that is sensitive to N-ethylmaleimide [Berkower, Leis &amp; Hurwitz (1973) J. Biol. Chem. 248, 5914-5921], was examined by using both site-directed mutagenesis and chemical modification. Novel aspects that were found are as follows. First, none of the cysteine residues is required for activity. Secondly, chemical modification of either Cys-13 or Cys-133 with thiol-blocking reagents inactivates the enzyme, but that of Cys-63 does not. Thus the sensitivity of E. coli RNAase H to N-ethylmaleimide arises not from blocking of the thiol group but from steric hindrance by the modifying group incorporated at either Cys-13 or Cys-133.</jats:p

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Biochemical Journal

Role of cysteine residues in ribonuclease H from <i>Escherichia coli</i>. Site-directed mutagenesis and chemical modification

http://www.biochemj.org/content/ppbiochemj/271/1/59.full.pdf

Role of cysteine residues in ribonuclease H from Escherichia coli. Site-directed mutagenesis and chemical modification

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