Purification and characterization of recombinant cell surface protein antigen A of Streptococcus sobrinus B13N

Abstract

1. 1. It has been reported that immunization of rhesus monkeys with the surface protein antigen I/II from Streptococcus mutans significantly reduced dental caries. 2. 2. The surface protein antigen A (SpaA) from Streptococcus sobrinus is known to correspond antigenically to I/II. MD51 is an Escherichia coli host containing pMD51, a plasmid encoding the SpaA gene from Streptococcus sobrinus B13N. 3. 3. The recombinant SpaA (rSpaA) was purified from cell extracts of Escherichia coli clone MD51. 4. 4. The purified recombinant SpaA was homogeneous with a molecular weight of 210 kDa according to SDS-PAGE and had an isoelectric point of 4.2 based on isoelectic focusing. 5. 5. Amino acid composition of rSpaA showed a relatively high amount of hydrophobic amino acids (39.7%).