Isotope labeled ε193 in complex with purified unlabeled θ interacts with β₂ only through the CBM. Superimposition of ¹⁵N-HSQC spectra of uniformly in vivo¹⁵N,¹³C-labeled ε193:unlabeled θ (black spectrum, selected resonance assignments in black) and of ε193:θ (27 µM) labeled specifically in ε193 with ¹⁵N-glutamine, threonine, serine, methionine, alanine and phenylalanine in the absence (blue spectrum) and presence (red spectrum) of β₂ (30 µM). Resonances were assigned as described in Materials and Methods. Cross-peaks were observed for 52 of 59 Gln, Thr, Ser, Met, Ala and Phe residues in the structured ε186 domain, and all were unaffected by addition of β₂ (selected signals labeled in purple); those of Ser2 and Thr3 in the disordered N-terminus could not be assigned, while Ala100, Thr128, Ser144, Ala164 and Thr179 had low intensity even in the absence of β₂. Signals in the CBM that broaden beyond recognition in the presence of β₂ (red spectrum; i.e., Gln182, Thr183, Ser184, Met185, Ala186, Phe187) are labeled in green, while assignments for flexible residues at the N- and C-termini (Ala4, Ala188 and Thr193) that are unaffected by β₂ are labeled in orange.