HSQC spectra of native Arg28/Arg45, Arg45Thr, Arg45Ser, and Arg28Ser peptides.
(A) Native Arg28/Arg45 peptide, with resonances corresponding to the initial unstructured sequence 1-20 and the loop regions between helices 46-52, 82-87, and 119-122 shown in black; resonances corresponding to the initial Helix C′ shown in yellow; and resonances corresponding to Helices A1, B1, and C1 of the triple helical bundle shown in red, green, and blue, respectively. Arrows denote resonances affected by the mutations, with black arrows noting the mutated residues (Arg45 and Arg28), red arrows noting resonances affected by the Arg45Thr mutation, and blue arrows noting resonances affected by the Arg45Ser mutation. (B) Arg45Thr peptide, with arrows noting resonances whose chemical shifts are affected by the mutation. (C) Arg45Ser peptide, with arrows noting resonances affected by the mutation. (D) Arg28Ser peptide, for which missing resonances can be seen by comparison with (A). All spectra were acquired for the samples in NMR sample buffer at 20°C.
