Evidence that an N-terminal S-layer protein fragment triggers the release of a cell-associated high-molecular-weight amylase in Bacillus stearothermophilus ATCC 12980.
AUTOR(ES)
Egelseer, E M
RESUMO
During growth on starch medium, the S-layer-carrying Bacillus stearothermophilus ATCC 12980 and an S-layer-deficient variant each secreted three amylases, with identical molecular weights of 58,000, 122,000, and 184,000, into the culture fluid. Only the high-molecular-weight amylase (hmwA) was also identified as cell associated. Extraction and reassociation experiments showed that the hmwA had a high-level affinity to the peptidoglycan-containing layer and to the S-layer surface, but the interactions with the peptidoglycan-containing layer were stronger than those with the S-layer surface. For the S-layer-deficient variant, no changes in the amount of cell-associated and free hmwA could be observed during growth on starch medium, while for the S-layer-carrying strain, cell association of the hmwA strongly depended on the growth phase of the cells. The maximum amount of cell-associated hmwA was observed 3 h after inoculation, which corresponded to early exponential growth. The steady decrease in cell-associated hmwA during continued growth correlated with the appearance and the increasing intensity of a protein with an apparent molecular weight of 60,000 on sodium dodecyl sulfate gels. This protein had a high-level affinity to the peptidoglycan-containing layer and was identified as an N-terminal S-layer protein fragment which did not result from proteolytic cleavage of the whole S-layer protein but seems to be a truncated copy of the S-layer protein which is coexpressed with the hmwA under certain culture conditions. During growth on starch medium, the N-terminal S-layer protein fragment was integrated into the S-layer lattice, which led to the loss of its regular structure over a wide range and to the loss of amylase binding sites. Results obtained in the present study provide evidence that the N-terminal part of the S-layer protein is responsible for the anchoring of the subunits to the peptidoglycan-containing layer, while the surface-located C-terminal half could function as a binding site for the hmwA.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=178397Documentos Relacionados
- The S-layer from Bacillus stearothermophilus DSM 2358 functions as an adhesion site for a high-molecular-weight amylase.
- Evidence that the N-terminal part of the S-layer protein from Bacillus stearothermophilus PV72/p2 recognizes a secondary cell wall polymer.
- The S-Layer Proteins of Two Bacillus stearothermophilus Wild-Type Strains Are Bound via Their N-Terminal Region to a Secondary Cell Wall Polymer of Identical Chemical Composition
- Evidence for an S-layer protein pool in the peptidoglycan of Bacillus stearothermophilus.
- High-Molecular-Weight Amylase Activities from Bacteria Degrading Starch-Plastic Films