Abstract
Surface protein layer (S layer) of Clostridium difficile GAI 1152 was a tetragonal array with each side of 7.8nm and interior angle of 77.8°, which was composed of the two protein subunits with respective molecular weights of 38kDa and 42kDa. The S layer protein subunits were directly isolated from the whole cells by simple procedures involving extraction of the whole cells with 6M GHCl and precipitation by 50% saturation with ammonium sulfate and purified by using DEAE-Sepharose CL-6B column chromatography followed by DEAE-5 PW equipped to HPLC. Amino acid analysis showed that both the subunits were acidic polypeptide and neither proline nor cysteine were present. The 38kDa subunit exhibited a single isoelectric form (pI 4.0), whereas the 42kDa subunit showed multiple isoelectric forms ranging from 5.5 to 6.3 of pI. Limited proteolysis of the both subunits with Staphylococcus aureus V8 enzyme showed quite dissimilar peptide maps between them, suggesting marked differences in primary structures.
