Production of recombinant proteins and purification steps.

<p>The upper part of the figure shows a scheme of the purification steps followed to prepare the three types of hetero-oligomers obtained in this work. The numbers indicate the corresponding lane of the representative stained gels shown below. Panel A shows a representative SDS-PAGE gel used for molecular mass estimation, including two sets of standards as indicated in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0050329#s2" target="_blank">Materials and Methods</a> section. Samples (30 µl) of key purification steps to produce wild type (B), mutated (C) and truncated MAT II (D) were prepared under standard reducing conditions for SDS-PAGE electrophoresis. Gel lanes correspond to: (1) refolded α2 (10 µg); (2) Q-Sepharose collected peak (10 µg); (3) concentrated Q-Sepharose peak (25 µg); (4) standards; (5) purified hetero-oligomer (10 µg); and (6) purified wild type (10 µg), mutant (5 µg) or truncated β subunit (10 µg). Panels B–D show only the relevant sections of the stained gels for each type of purification; the positions for the 45 and 31 kDa protein standards are indicated on the side of the gels. Dots indicate places where gel lanes have been cropped for clarity.</p>