Molecular analysis of the S-layer protein of the uranium mining waste pile isolate Bacillus sphaericus JG-A12

Cells of the uranium mining waste pile isolate Bacillus sphaericus JG-A12 are capable of selective and reversible accumulation of heavy metals.
The cells of B. sphaericus JG-A12 are enveloped by a surface-layer (S-layer). S-layers, which are composed of identical protein monomers with the ability to self-assemble into two-dimensional crystalline arrays, are one of the most commonly observed surface structures of archaea and bacteria.
In case of the strain JG-A12 our analyses showed that the S-layer is capable of binding metals. Thus, it is probable that the S-layer contributes to heavy metal resistance.
Sequence analyses showed, that the S-layer proteins of B. sphaericus JG-A12 and its closest relative, B. sphaericus NCTC9602, possess an unusual high identity of the N-terminus and the central domain, whereas the C-terminal parts differ significantly between the two strains. Further, both strains contain a second truncated S-layer gene-like copy which is possibly encoded by large plasmids. These results indicate a horizontal transfer of parts of the gene between different strains.
The S-layer proteins show a high content of aspartate and glutamate, especially in the C-terminal part. IR analyses demonstrated that the carboxylgroups of these residues are involved in Pd-binding.

VAAM 2004
Braunschweig 28.03.-31.03.2004