InterPro: IPR002125 CMP/dCMP deaminase, zinc-binding

Cytidine deaminase (EC:3.5.4.5) (cytidine aminohydrolase) catalyzes the hydrolysis of cytidine into uridine and ammonia while deoxycytidylate deaminase (EC:3.5.4.12) (dCMP deaminase) hydrolyzes dCMP into dUMP. Both enzymes are known to bind zinc and to require it for their catalytic activity [1, 2]. These two enzymes do not share any sequence similarity with the exception of a region that contains three conserved histidine and cysteine residues which are thought to be involved in the binding of the catalytic zinc ion.

Such a region is also found in other proteins [3, 4]:

• Yeast cytosine deaminase (EC:3.5.4.1) (gene FCY1) which transforms cytosine into uracil.
• Mammalian apolipoprotein B mRNA editing protein, responsible for the postranscriptional editing of a CAA codon into a UAA (stop) codon in the APOB mRNA.
• Riboflavin biosynthesis protein ribG, which converts 2,5-diamino-6-(ribosylamino)-4(3H)-pyrimidinone 5'-phosphate into 5-amino-6-(ribosylamino)-2,4(1H,3H)-pyrimidinedione 5'-phosphate.
• Bacillus cereus blasticidin-S deaminase (EC:3.5.4.23), which catalyzes the deamination of the cytosine moiety of the antibiotics blasticidin S, cytomycin and acetylblasticidin S.
• Bacillus subtilis protein comEB. This protein is required for the binding and uptake of transforming DNA.
• B. subtilis hypothetical protein yaaJ.
• Escherichia coli hypothetical protein yfhC.
• Yeast hypothetical protein YJL035c.