Back to Search
Start Over
Chlamydial ribonucleotide reductase: Tyrosyl radical function in catalysis replaced by the FeIII-FIV cluster.
- Source :
- Proceedings of the National Academy of Sciences of the United States of America; 6/27/2006, Vol. 103 Issue 26, p9850-9854, 5p, 1 Diagram, 3 Graphs
- Publication Year :
- 2006
-
Abstract
- Ribonucleotide reductase (RNR) from Chlamydia trachomatis is a class I RNR composed of proteins R1 and R2. In protein R2, the tyrosine residue harboring the radical that is necessary for catalysis in other class I RNRs is replaced by a phenylalanine. Active C. trachomatis RNR instead uses the Fe<superscript>III</superscript>–Fe<superscript>IV</superscript> state of the iron cluster in R2 as an initiator of catalysis. The paramagnetic Fe<superscript>III</superscript>–Fe<superscript>IV</superscript> state, identified by <superscript>57</superscript>Fe substitution, becomes electron spin resonance detectable in samples that are frozen during conditions of ongoing catalysis. Its amount depends on the conditions for catalysis, such as incubation temperature and the R1/R2 ratio. The results link induction of the Fe<superscript>III</superscript>–Fe<superscript>IV</superscript> state with enzyme activity of chlamydial RNR. Based on these observations, a reaction scheme is proposed for the iron site. This scheme includes (i) an activation cycle involving reduction and an oxygen reaction in R2 and (ii) a catalysis cycle involving substrate binding and turnover in R1. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00278424
- Volume :
- 103
- Issue :
- 26
- Database :
- Complementary Index
- Journal :
- Proceedings of the National Academy of Sciences of the United States of America
- Publication Type :
- Academic Journal
- Accession number :
- 21579482
- Full Text :
- https://doi.org/10.1073/pnas.0600603103