Fig. 3

In vitro dimerization of KfrA proteins from R751 and RA3 plasmids in a parallel fashion. a The purified His-tagged KfrA proteins (0.1 mg ml^− 1) were incubated with different concentrations of glutaraldehyde (GA) for 20 min at room temperature and the products were separated on 12% SDS-polyacrylamide gel. Dimers, tetramers and other higher order complexes are indicated by arrows. M- protein markers. b Mass spectrometry analysis of KfrA proteins. Free cysteines were covalently blocked with iodoacetamide followed by reduction of disulfide bonds and tagging of the cysteines with methyl methanethiosulfonate. After tryptic digestion of protein, the peptides were subjected to MS/MS analysis. Selected spectra of cysteine-containing peptides identified with highest score are presented. Amino acids preceding ATG codon of KfrAs correspond to N-terminal extension of His-tagged proteins. Modifications resulting from reaction with the cysteine-blocking agents: CAM – Carbamidomethyl; MA – Methylthio are marked. c Schematic representation of KfrA homodimer with monomers in parallel arrangement