The interaction was labile to oxidants, such as diamide Bcl 2 inhibitor and menadione. Based on these data, NCgl0899 was named spiA (stress protein interacting with WhcA). Physical association and dissociation of the purified His6–WhcA and GST–SpiA fusion proteins, as assayed by in vitro pull-down experiments, were consistent with in vivo results. These data indicated that the

interaction between WhcA and SpiA is not only specific but also modulated by the redox status of the cell and the functionality of the WhcA protein is probably modulated by the SpiA protein. Corynebacterium glutamicum is a Gram-positive bacteria that belongs to the order Actinomycetales, which also includes the genera Mycobacterium and Streptomyces (Ventura et al., 2007). Corynebacterium glutamicum is a remarkable organism and is capable of producing a variety of amino acids and nucleotides in large quantities (Leuchtenberger et al., 2005). Because of the industrial importance of this organism, its relevant genetic and biochemical features have been extensively characterized. Accordingly, strategies that C. glutamicum cells adopt in response to cellular stresses have attracted scientific interests in recent years. WhiB-like genes are a class of genes that perform diverse cellular processes, such as cell division, differentiation, pathogenesis, starvation survival, and stress

response (Gomez, 2000; Steyn et al., 2002; FXR agonist Kim et al., 2005; Geiman et al., 2006; Raghunand & Bishai, 2006; Singh et al., 2007; Choi et al., 2009). The whiB gene, which was originally identified and characterized in Streptomyces coelicolor, is a developmental regulatory gene that is essential for the sporulation of aerial hyphae (Davis & Chater, 1992). The whiB homologues are only found in the order Actinomycetales. Seven whiB homologues have been identified in the Mycobacterium tuberculosis

genome and at least six are present in S. coelicolor (Soliveri et al., 2000), whereas only four are found in C. glutamicum (Kim et al., 2005). The WhiB-like Liothyronine Sodium proteins have four conserved cysteine residues that bind to a redox-sensitive Fe–S cluster (Jakimowicz et al., 2005; Alam et al., 2007; Singh et al., 2007; Crack et al., 2009; Smith et al., 2010), which plays a critical role in controlling protein function. In general, the cluster loss reaction followed by oxidation of the coordinating cysteine thiols that form disulfide bridges is important for activity. For example, S. coelicolor WhiD loses its Fe–S cluster upon exposure to oxygen (O2) and the apo-WhiD may play important roles in cell physiology (Crack et al., 2009). Some WhiB-like proteins may function as transcription factors, as suggested by the presence of predicted helix–turn–helix DNA-binding motif. Recently, the M. tuberculosis WhiB1 protein in its apo-form was shown to have DNA-binding activity (Smith et al., 2010).