Issue Date: May 28, 2007
Enzyme Gets Metal Makeover
An unprecedented manganese-iron cofactor is at the heart of a human pathogen's ribonucleotide reductase (RNR) enzyme, according to a new study (Science 2007, 316, 1188). RNRs provide all organisms with the 2′-deoxyribonucleotide building blocks needed to synthesize DNA. The human version of this enzyme uses a diiron cofactor to generate a tyrosine radical, which in turn generates a cysteine radical that initiates the conversion of 2′-ribonucleotides into 2′-deoxyribonucleotides. It's been suggested that Chlamydia trachomatis and several other human pathogens cut out the tyrosine radical step and instead use their diiron cofactor to create the crucial cysteine radical. A team led by Carsten Krebs and J. Martin Bollinger of Pennsylvania State University has now published spectroscopic and enzymatic activity evidence that suggests C. trachomatis' metal cofactor actually contains both manganese and iron. The surprising result suggests that this and other human pathogens may have evolved novel RNRs as an adaptation to their host's immune response, they note. Such enzymes could present specific targets for antibacterial design, Bollinger says.
- Chemical & Engineering News
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