Table 1.

Populations of in/out/tethered gates for K66 or K66A single α₇-ring particles, either unbound or 11S RP bound

α7 Construct	α7:11S	Leu81	Met-1
		Bound*	In	Out	In/out	Tethered
M1I+M6A+S95C α7	1:0	0%	27.3 ± 1.1%	72.7 ± 2.8%	0.38 ± 0.02	0%
	1:3	89 ± 3%	12.0 ± 0.8%	24.4 ± 4.0%	0.49 ± 0.09	63.6 ± 4.5%
M1I+M6A+K66A+S95C α7	1:0	0%	27.3 ± 1.0%	72.7 ± 3.2%	0.38 ± 0.02	0%
	1:3	3 ± 2%	23.2 ± 1.7%	57.7 ± 2.4%	0.40 ± 0.03	19.2 ± 1.1%

Observed populations were calculated from peak volumes and converted to populations of the five states highlighted in Fig. 2B, as described in the text. Peak volumes were corrected for differential transverse relaxation in the case of M-1 (see Materials and Methods for details).

^*Percent 11S RP bound, as reported by ratio of volumes of “bound” and “free” L81δ1 peaks (Fig. 2 A and B). The chemical shift of L81δ1 responds to an interaction involving the C-terminal tail of the 11S RP and α-subunit residues 78 to 82. In the case of WT α₇-rings, these contacts are present, and hence L81δ1 is a good probe of binding. In the case of the K66A mutant, the binding interaction reported by L81 is no longer present (no CSP; see text). Binding can still occur, however, through a second interaction discussed in the text, and the fraction bound determined as described in the text and Materials and Methods.