Myosin shifts into reverse gear.

213 news & views time to useful timescales. By manipulating the ratio of these modified monomers, Rant and co-workers created nanopores that contained only a single nitrilotriacetic acid group within the sensing zone of the nanopore, which could be used to detect the reversible binding of single proteins. In another part of the study, Rant and colleagues functionalized a nanopore with three nitrilotriacetic acid groups and showed that this nanopore could tightly capture Protein A, which is a clinically relevant pathogenic molecule that evades the immune system by binding to different antibodies with different affinities. The nanopores that contained Protein A were used as an assay to discriminate between different types of rodent antibodies — each type of antibody that entered the nanopore would bind to Protein A with a different affinity, resulting in a characteristically different electrical fingerprint. This forms a useful assay for studying protein– protein interactions. A major limitation of this technique is that most naturally occurring proteins do not have polyhistidine tags. Although the mechanics and biophysics of key proteins can still be investigated once the protein is given such a tag, this method in its current form cannot be used as a biosensor to detect clinical targets directly. Despite this limitation, direct observation of single proteins has great potential for many applications, including ultrasensitive detection and enzyme kinetic measurements. Furthermore, the assay can be used to quantify the strength of molecular interactions, and could offer improvements over traditional immunoblotting methods. This is the first time that reversible detection of single proteins has been demonstrated using a synthetic nanopore, and this technique helps solidify synthetic nanopores as an important research tool. ❐ C ytoskeletal motor proteins moving along filamentous tracks perform a variety of functions within cells in a highly energy-efficient manner, and can be easily modified by the tools of molecular biology. This makes them promising candidates for use as force-generating elements in nanotechnology. However, controlling them in an artificial environment is a significant challenge. For example, a molecular motor usually moves in just one direction, and it would be useful to be able to make it move along its track in both directions. Writing in Nature Nanotechnology, Zev Bryant and colleagues 1 at Stanford University now report a controllable, bidirectional motor protein based on myosin VI. Myosin VI is a motor protein that plays a role in intracellular processes such as endocytosis, secretion and …