Main > PROTEINS > Structure. > NMR Structure of LARGER Proteins > Org.: JP. T. (SAIL/Patent) > SAIL Description

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Protein properties and interactions are often studied through nuclear magnetic resonance (NMR) spectrometry, which can provide 3-D solution structures of proteins. But it s currently difficult to elucidate NMR structures of large proteins because their spectra are too complex. At present, fewer than 2% of all NMR structures in the Protein Data Bank have masses exceeding 25 kDa, whereas many proteins weigh in at hundreds of kilodaltons.

Stereo-array isotope labeling (SAIL) could now ameliorate this problem. Author, developed the technique and report its use to determine the structure of a 41-kDa protein.

In SAIL, chiral organic synthesis is used to prepare amino acids labeled with deuterium, carbon-13, and nitrogen-15 in a highly stereo- and regiospecific manner, and a protein is then synthesized from the labeled amino acids. The NMR spectrum of the resulting SAIL protein is simpler, less congested, and more easily interpretable than that of the corresponding conventional protein. Author and coworkers believe the approach should make it possible to routinely solve the structures of proteins at least twice as large as those commonly determined today by NMR.

Drawbacks are that the labeled amino acids are difficult to synthesize and must be incorporated into proteins by in vitro cell-free protein synthesis, which is not easy to carry out. But a Org.-based venture company, with Japanese government support, is being set up to supply SAIL amino acids commercially. Author and coworkers are also trying to fully automate SAIL-based structure determination and to push the technique s molecular-weight limits ever higher.




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