Clayton et al. 10.1073/pnas.0711533105.

Supporting Information

Files in this Data Supplement:

SI Figure 6
SI Figure 7
SI Figure 8
SI Table 1
SI Table 2
SI Figure 9




SI Figure 6

Fig. 6. Stereoviews of part of S6 (Upper) and S3 (Lower) from the MlotiK1 channel structure. Molecules are shown in stick representation. Experimental, 4-fold averaged, sharpened maps are shown as a mesh. Some residues are labeled for reference.





SI Figure 7

Fig. 7. Superposition of S4-S5 linker and part of S4, S5, and S6 TMs from MlotiK1 (red) and Kv1.2 (cyan). Some residues in the linkers are shown as stick representation.





SI Figure 8

Fig. 8. Sequence alignment of Kv1.2, KvAP channels, MlotiK1, RpalK, and three other prokaryotic channels of the cyclic nucleotide-regulated channel family: MspiK1 channel from Magnetospirillum magnetotacticum (GB: AAAP01003723.1) and the BjapK1 and BjapK2 channels from Bradyrhizobium japonicum (GI:27355938 and GI: 27354013). Residues shown in blue correspond to TM helical regions, as defined in the MlotiK1, KvAP, and Kv1.2 structures. Residues in red correspond to the S4-S5 linker. KvAP residues in green are most probably the linker but are either part of S4 in the isolated voltage sensor structure or part of S5 in the whole channel structure. Important positively charged S4 residues are shown in bold. Important countercharges that are absent in MlotiK1 S2 are indicated by stars. The important countercharge that is conserved in MlotiK1 S3 is indicated by the arrowhead. The pore helices and the selectivity filters are underlined. The C termini were not included in the alignment.





Table 1. X-ray data statistics

Crystal

Native

RbCl cocrystal

CsCl cocrystal

Resolution, Å

3.1

3.4

4.2

R

meas, %

14.3

8.7

13.9

Multiplicity

4

3.8

3.7

Completeness, %

99.5

99.2

99.4

I/SigI, overall

9.0

13.9

4.8

I/SigI, high-resolution shell

1.0

2.7

1.6

N/A, not applicable.





Table 2. Model refinement statistics

Resolution, Å

3.1

R

 factor work/free, %

27.6 / 28.6

Ramachandran plot residues, %

Favored: 91.8

 

Additional: 7.8

 

Generous: 0

 

Disallowed: 0.4

rmsd bond lengths

0.006 Å

rmsd bond angles

0.898°

There are four disallowed residues in the MlotiK1 structure: Phe-114 in subunits A, B, C, and D. These residues are in the N-terminal end of the S4-S5 linker and are tightly packed against the S5 helix of the neighboring subunit. It seems that the packing arrangement forces the main chain torsional angles to an unfavorable region.





SI Figure 9

Fig. 9. The S4 helix. (A) Stereoview of S4 from MlotiK1. An experimental, 4-fold-averaged and sharpened map is shown in a red mesh. All residues are shown in stick representation. The main chain is also shown as a red ribbon. Some residues are labeled for reference. (B) Stereoview of S4 helix in MlotiK1. The main chain hydrogen-bonding network is shown as dotted lines. Distances between donor and acceptor atoms are indicated in angstroms. Some residues are labeled for reference.