ABCG2 and infection: For example, during the process of human infection with Streptococcus agalactiae CS101, the Opp (oligopeptide) ABC transporters, which are involved in amino acid intake, heme synthesis, spore formation, and the expression of the major virulence factor SpeB cysteine protease, were observed to reduce the expression of fibrinogen-binding protein (FbsA), indicating a decrease in the adhesion of the CS101 strain to epithelial cells [30].