Properties of the purified hexahistidine-tagged BioG and BioGC proteins.

aMolecular weight was determined by MALDI-mass spectrometry accurate to within ∼1% except BioGC which was determined by electrospray mass spectrometry. The N-terminal sequence of the N-terminally hexahistidine-tagged C. jejuni BioG is Met-Gly-Ser and thus as expected from the specificity of E. coli methionine aminopeptidase {Xiao, 2010 #7} the protein lacks the N-terminal methionine residue. The calculated value is for the species lacking methionine.bSolution structures were assayed by size exclusion chromatography. Each of the BioG proteins eluted between bovine erythrocyte carbonic anhydrase (29 kDa) and horse myoglobin (17 kDa) standards indicating monomeric proteins. The BioGC protein eluted between chicken ovalbumin (44 kDa) and bovine serum albumin (66 kDa) indicating that the protein is a monomer in solution. Note that upon concentration for application to the size exclusion column B. fragilis BioGC formed aggregates although an appreciable fraction of the protein eluted at the volume expected for a monomeric protein (between bovine serum albumin and there was no apparent peak where dimer would elute. The fast eluting peaks were identified as BioGC aggregates by SDS-PAGE.