The complete nucleotide sequence of the ami locus of Streptococcus pneumoniae revealed the presence of six open reading frames, amiABCDEF. The predicted Ami proteins are probably involved in a transport system. The AmiA, C, D, E, and F proteins exhibit homology with components of the oligopeptide permeases (opp) of Salmonella typhimurium and Escherichia coli. Intriguingly, the AmiB protein is homologous to ArsC, a cytosolic modifier subunit of the anion pump encoded by the arsenical resistance operon of the R-factor R773 from E. coli. Data are presented which indicate that Ami is indeed a transport system.