Functional activity of MtbC406S mutated protein.

(A) LC-ESI-MS of DTT reduced MtbC406S digested with trypsin and chymotrypsin. The m/z 760.9 shows the substitution of Cys⁴⁰⁶ to Serine⁴⁰⁶. (B) (a) MtbC406S protein: MALDI TOF analysis, in the positive ion detection mode. No peaks are obtained at 691 (M+H)⁺ and 713 (M+Na)⁺ for c-di-GMP, 709 (M+H)⁺ and 731 (M + Na)⁺ for pGpG (b) MtbDGC protein for control: MALDI TOF analysis, in the positive ion detection mode, ions were detected at 691 (M+H)⁺ and 713 (M+Na)⁺ for c-di-GMP (c) 709 (M+H)⁺ and 731 (M + Na)⁺ for pGpG.