Rapid 4-D Imaging Focused on Protein Folding

With rapid 4-D imaging, NIST scientists at JILA (Joint Institute for Laboratory Astrophysics, Boulder, Col.) are able to study the higher-order structure of proteins for the first time. In one example, the higher-ordered structure of bacteriorhodopsin was found to have 14 intermediates. This is seven times more than was previously reported using conventional technology. The ability to see short-lived individual states is important in understanding the structure–activity relationship of proteins; in this case, bacteriorhodopsin is a light-sensitive proton pump.

In order to become an enzyme and to fulfill its biological role, a protein must adopt a specific 3-D structure. If the structure is not right, the protein may not function, or worse, become toxic, as in a prion.

The JILA team developed an atomic force microscope with nanometer resolution that measures the force required to stretch the enzyme. By recording the extension force and speed on bacteriorhodopsin, the researchers found a series of plateaus that indicate a stable intermediate structure as the enzyme is stretched (Figure 1). These spatiotemporal states may last only a few microseconds, but the microscope provided a tenfold improvement in measurement of force and is 100 times faster than previously used methods.1

Figure 1 – Infrared laser light senses motion of the cantilever tip of an atomic force microscope as it scans over a protein surface (lower left), producing a signal (upper right). The signal shows the rapid conversion between two states within less than a millisecond. (Image courtesy of JILA.)

Reference

  1. http://science.sciencemag.org/content/355/6328/945

Robert L. Stevenson, Ph.D., is Editor Emeritus, American Laboratory/Labcompare; e-mail: [email protected].

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