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Biochimie. 1998 Oct;80(10):855-61.

Bioaccumulation of heavy metals with protein fusions of metallothionein to bacterial OMPs.

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Departament de Genètica, Universitat de Barcelona, Spain.


In view of potential biotechnological applications, eukaryotic metallothioneins (MTs) have been expressed in Escherichia coli as fusions to membrane or membrane-associated proteins such as LamB, the peptidoglycan-associated lipoprotein protein (PAL) or a hybrid Lpp/OmpA carrier sequence. The use of different anchors enables the MT moiety to be targeted into various cell compartments thus bringing the metal-binding ability of the resulting hybrids to specific sites of the cell structure. To this end, both full-size and partial sequences of the human or mouse MTs have been genetically fused to: i) the permissive site 153 of the LamB sequence, which loops out the MT to the external medium; ii) the N-terminus of a PAL variant devoid of its N-terminal cystein, which targets expression of the fusion into the periplasm; and iii) the C-terminus of Lpp-OmpA, for anchoring the MT to the outer membrane protein as an N-terminal fusion. Each type of fusion presented a distinct behavior in terms of expression, stability and ability to endow E. coli cells an enhanced accumulation of Cd2+, in good correlation with the number of metal-binding centers contributed by the MT moiety of the fusions. The expression in vivo of metalloproteins bound to bacterial envelope structures opens a way to design biomass with specific metal-binding properties.

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