Fimbriae (also called pili), polar filaments radiating from the surface of the bacterium to a length of 0.5-1.5 micrometers and numbering 100-300 per cell, enable bacteria to colonize the epithelium of specific host organs. A minor fimbrial subunit, this protein is necessary for full expression of S-specific binding. S-fimbrial adhesins enable pathogenic E.coli causing urinary-tract infections or newborn meningitis to attach to glycoproteins terminating with alpha-sialic acid-(2-3)-beta-Gal. This protein binds to the alpha-sialic acid-(2-3)-beta-Gal and is thus responsible for erythrocyte recognition and hemagglutination. Deletion prevents hemagglutination (erythrocyte recognition), although cells are still poorly fimbriated. Belongs to the fimbrial protein family.