Fig. 1.

NMR characterization of PLN pentamer. (A) SDS/PAGE of PLN reconstituted in 200 mM DPC and SDS under reducing conditions. Lane 1 shows the molecular mass marker. In lanes 2 and 3, PLN was reconstituted in DPC and SDS, respectively, and was loaded on the gel without boiling. For lane 4, the DPC-reconstituted sample was boiled for 30 min before loading and pentamers were disrupted. The PLN concentration (0.02 mM) is the same in lanes 2-4. (B) A 750-MHz ¹H-¹⁵N transverse relaxation-optimized spectroscopy spectrum of 0.2 mM PLN pentamer in DPC. Each peak represents a backbone NH moiety with residue number labeled. The C5 rotational symmetry is manifested in the presence of one set of 50 amide peaks. (C) The products of ¹⁵N longitudinal (R₁) and transverse (R₂) relaxation rates used to probe variations in chemical exchange (26); the rates were recorded at ¹H frequency of 600 MHz by using experiments that closely followed that of Farrow et al. (45). (D) The different ratios of R₂ to R₁ for AP and TM helices indicate that the AP helices are mobile relative to the TM helices in the pentamer.