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chrR6 Chromate Reductase Enzyme

The chrR6 protein is a mutated/enhanced version (Tyr128Asn) of the chrR enzyme originally found in Escherichia coli. It has chromate and uranyl reductase activity.

Usage and Biology

The chrR6 enzyme is a mutated/enhanced version (^Tyr128^Asn) of the soluble chrR enzyme originally found in Escherichia coli and Pseudomonas putida. It has chromate and uranyl reductase activity. The enzyme chrR6 reduces Cr(VI) directly to Cr(III) without producing an unstable Cr(V) intermediate and minimizing generation of toxic reactive oxygen species. [1]

As determined from studies on purified enzymes, ^Tyr128^Asn substitution increases the rate of Cr(VI) reduction from 295 ± 27 nmol mg protein^-1 min^-1, as observed for chrR, to 8,812 ± 611 nmol mg protein^-1 min^-1. K_cat/K_m values are 4.5 × 10⁴ ± 3 × 10³ for chrR and 1.3 × 10⁷ ± 3 × 10⁵ for chrR6. When the activity of chrR6 and chrR was studied in vivo in soil bacteria P. putida, no enhanced chromium or uranium reduction activity was observed for chrR6, indicating that the permeability barrier prevents the reduction activity.

[1] Barak, Y. et al. “Analysis of Novel Soluble Chromate and Uranyl Reductases and Generation of an Improved Enzyme by Directed Evolution.” Applied and Environmental Microbiology 72.11 (2006): 7074–7082. Web.

Sequence and Features