Toward a Halophenol Dehalogenase from Iodotyrosine Deiodinase via Computational Design

Reductive dehalogenation offers an attractive approach for removing halogenated pollutants from the environment, and iodotyrosine deiodinase (IYD) may contribute to this process after it can be engineered to accept a broad range of substrates. The selectivity of IYD is controlled in part by an active site loop of ∼26 amino acids. In the absence of a substrate, the loop is disordered and only folds into a compact helix-turn-helix upon halotyrosine association. The design algorithm of Rosetta was applied to redesign this loop for response to 2-iodophenol rather than iodotyrosine. One strategy using a restricted number of substitutions for increasing the inherent stability of the helical regions failed to generate variants with the desired properties. A series of point mutations identified strong epistatic interactions that impeded adaptation of IYD. This limitation was overcome by a second strategy that placed no restrictions on side-chain substitution by Rosetta. Nine representative designs containing betw...