Understanding ion channels: The Cysteine Scanning Accessibility Method for eejits - Part The Second (in which I ruggedly persevere in my efforts to avoid actually talking about the Cysteine Scanning Accessibility Method)

Figure 1. Thiol group of cysteine side chain can be covalently modified. Top shows the formation of a disulfide bond between two Cys side chains. Bottom shows covalent modification of a Cys side chain by MTSET+, a water-soluble thiol-reactive chemical.What's so hot about Cysteine?Short story: we can stick things to it.Long story: The amino acid Cysteine (Cys, or "C") contains a thiol group within its side chain, which can form covalent bonds with thiol-reactive  and thiol group-containing molecules. In proteins, cysteine side chains that come into close proximity to one another, whether on the same or separate polypeptides, can react together to form a strong, covalent disulfide bridge (Figure 1). These bridges are essential for assembly and normal folding of a multitude of proteins. However, free Cys side chains can also be modified by exposure to water-soluble thiol-reactive agents, such as the MTSET+ molecule shown in Figure 1 or ionic silver (Ag+), providing a means by which to ascertain if a particular Cys side chain is exposed to the bulk aqueous environment (as opposed to embedded in protein or lipid). If the side chain is accessible, the thiol-reactive molecule will dump an extra R group on it, thereby altering the protein structure in a manner that could potentially influence its function (e.g. change its enzymatic activity, or in the case of an ion channel, change the way it opens and closes, or c...
Source: Across the Bilayer - Category: Medical Scientists Tags: Science IonChannels Source Type: blogs