Corrections and clarifications.
Figure 4 of the report "Selective and ATP-dependent translocation of peptides by the MHC-encoded peptide transporter" by J. J. Neefjes, F. Momburg, and G. J. Hammerling (6 Aug., p. 769) stated incorrectly that a peptide with T as the COOH-terminal residue was not efficiently translocated. Resynthesis revealed that the peptide RYWANATRST is transported by rat TAP. This does not change the general conclusion that the transporters are selective, because several other peptides are not well translocated [F. Momburg et al., Nature 367, 648 (1994)].