Engineering outer-membrane proteins in Pseudomonas putida for enhanced heavy-metal bioadsorption

Metallothioneins (MTs) are small, cysteine-rich proteins with a strong meta l-binding capacity that are ubiquitous in the animal kingdom. Recombinant e xpression of MT fused to outer-membrane components of Gram-negative bacteri a may provide new methods to treat heavy-metal pollution in industrial sewa ge. In this work, we have engineered Pseudomonas putida, a per se highly ro bust microorganism able to grow in highly contaminated habitats in order to further increase its metal-chelating ability. We report the expression of a hybrid protein between mouse MT and the beta domain of the IgA protease o f Neisseria in the outer membrane of Pseudomonas cells. The metal-binding c apacity of such cells was increased three-fold. The autotranslocating capac ity of the beta domain of the IgA protease of Neisseria, as well as the cor rect anchoring of the transported protein into the outer membrane, have bee n demonstrated for the first time in a member of the Pseudomonas genus. (C) 2000 Elsevier Science Inc. All rights reserved.