Expression, Purification, and In Silico Characterization of Mycobacterium smegmatis Alternative Sigma Factor SigB

Figure 2

IPTG concentration optimization for the expression of recombinant His-SigB. (a) 10% SDS PAGE depicting recombinant His-SigB protein expression profile in CodonPlus (DE3) host strain. The highest protein expression is observed in 0.1 mM IPTG. (b) Solubility of the recombinant His-SigB in different IPTG concentrations at 37°C. 10% SDS PAGE depicting recombinant His-SigB protein distribution in cell pellet and supernatant in CodonPlus (DE3) induced with IPTG concentration from 0.05 to 0.5 mM IPTG. The highest protein solubility observed in the supernatant fraction at 0.1 mM IPTG. M: molecular size marker; V.O.: pET28a vector only control; V.O.I: pET28a vector only induced; U: uninduced His-SigB clone; P: pellet; S: supernatant. (c) Gel-based semiquantitative analysis from (a) also depicts the highest expression of His-SigB at 0.1 mM IPTG concentration. (d) Semiquantitative analysis from (b) depicts higher relative protein solubility observed in the supernatant fraction at 0.1 mM IPTG. Semiquantitative analysis of the gels was performed with Quantity One software (BIO-RAD).

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