Bacterial expression, purification and biophysical characterization of wheat germ agglutinin and its four hevein-like domains.

Wheat germ agglutinin (WGA), a chitin binding lectin, has attracted increasing interest because of its unique characteristics such as conformational stability, binding specificity and transcytosis capacity. To pave the way for the study of the molecular basis of WGA's structural stability and binding capacity, as well as to facilitate its use in biomedical and biotechnological developments, we produced recombinant WGA and its 4 isolated hevein-like domains in a bacterial system. All the proteins were expressed as fusion constructs linked to a thioredoxin domain, which was enzymatically or chemically released.

Recognition of peptidoglycan and β-lactam antibiotics by the extracellular domain of the Ser/Thr protein kinase StkP from Streptococcus pneumoniae.

The eukaryotic-type serine/threonine kinase StkP from Streptococcus pneumoniae is an important signal-transduction element that regulates the expression of numerous pneumococcal genes. We have expressed the extracellular C-terminal domain of StkP kinase (C-StkP), elaborated a three-dimensional structural model and performed a spectroscopical characterization of its structure and stability. Biophysical experiments show that C-StkP binds to synthetic samples of the cell wall peptidoglycan (PGN) and to β-lactam antibiotics, which mimic the terminal portions of the PGN stem peptide.