Rv2607 from Mycobacterium tuberculosis Is a Pyridoxine 5′-Phosphate Oxidase with Unusual Substrate Specificity
Figure 2
Nano-ESI mass spectrum of intact Rv2607 with co-purified FMN.
The major species, C, has peaks with charges ranging from 15+ to 12+ in the 3500-4500 m/z range that correspond to a molecular weight of 55376±12. This experimental mass is consistent with the calculated mass for the complex of dimeric Rv2607 with one molecule of FMN bound (55442 Da), which is derived from the amino acid sequence of the 6x-histidine tagged Rv2607 (54986 Da; 27493 Da per protomer) and the molecular weight of FMN (456 Da). Monomeric tagged Rv2607 and truncated Rv2607 monomer (missing 10-11 residues), are present in solution and correspond to molecular weights of A (27450±52 Da) and B (26215±54 Da) respectively. A minor dimeric species comprised of full length and truncated monomer is represented as species D. Higher molecular weight oligomers (trimers E and tetramers F with molecular weights of 110.6 and 82.7 kDa, respectively) are electrospray-induced non-specific association of monomers and dimers.