Structure of the cytosine–cytosine mismatch in the thymidylate synthase mRNA binding site and analysis of its interaction with the aminoglycoside paromomycin

Imino–amino region in the NOESY of TSMC in H₂O recorded at 5°C. Selected assignments are labeled in the spectrum. Key NOE contacts (C16H6-G6NH1 and C5H6-G17NH1) designated with asterisks, provide direct evidence that the cytosine bases in the CC mismatch are internal. The NOE between C20H6 and G1NH1 protons in the first GC base pair peak were not observed, likely due to fast breathing motions of the terminal residues of TSMC.