Structural Analysis of Proteins from Bacterial Secretion Systems and Their Assemblies by NMR Spectroscopy.

Bacterial secretion systems are built up from proteins with different physicochemical characteristics, such as highly hydrophobic transmembrane polypeptides, and soluble periplasmic or intracellular domains. A single complex can be composed of more than ten proteins with distinct features, spreading through different cellular compartments. The membrane and multicompartment nature of the proteins, and their large molecular weight make their study challenging. However, information on their structure and assemblies is required to understand their mechanisms and interfere with them. An alternative strategy is to work with soluble domains and peptides corresponding to the regions of interest of the proteins.Here, we describe a simple and fast protocol to evaluate the stability, folding, and interaction of protein sub-complexes by using solution-state Nuclear Magnetic Resonance (NMR) spectroscopy. This technique is widely used for protein structure and protein-ligand interaction analysis in solution.