Preparative SDS-PAGE of SDS-extract from Streptococcus gordonii PK488 and identification of MUC7 binding proteins. Twenty milligrams of the surface extract from S. gordonii was electrophoresed on a 7.5% preparative electrophoresis in a Bio-Rad mini-prep cell and (A) selected fractions were electrophoresed on 7.5% SDS-PAGE gels, proteins visualized with silver stain. (B) Selected fractions were transferred onto nitrocellulose membranes by slot blotting and probed with MUC7 preparation. MUC7 binding was determined by immunoblotting as described in Material and Methods. Positions of molecular weight markers are indicated (kDa).