|Home | About | Journals | Submit | Contact Us | Français|
The development of the autoinduction process by Studier has greatly streamlined bacterial protein expression. In autoinduction media, bacterial expression systems controlled by lac promoters (such the pET system) grow uninduced to a high cell density and then spontaneously induce high-level protein expression without the need to monitor cell density or add isopropyl β-D-1-thio-galactopyranoside (IPTG). These media offer significant increases in target protein yield compared to conventional IPTG induction. Autoinduction media are ideally suited for high-throughput, parallel analysis of protein expression, solubility screening, and purification from multiple expression clones. Here we describe a new autoinduction medium that enables production of [U-15N] and [U-13C, U-15N]-labeled proteins for NMR structural studies. We expressed and purified four [U-15N]-labeled target proteins and one [U-15N, U-13C]-labeled protein from Arabidopsis clones using this medium. NMR analysis of each labeled protein returned high-quality HSQC spectra with greater than 95% isotope incorporation, as calculated from mass-spectrometric data. The isotopic labeling medium (Overnight Express NMR) can generate labeled proteins from colonies in two work days, and will soon be commercially offered as pre-sterilized, ready to use solutions.