Table 2.
Ligand and His64 conformations and occupancies for the MbCNR structures.
| CNR complex | space group | crystal pH | resolution (Å) | His64 rotomer | His64 occupancya | His64-Nε to CNR-N (Å) | His64-Nδ to Asp60-O′ (Å) | CNR rotomer | CNR occupancyb | FTIR Finc |
|---|---|---|---|---|---|---|---|---|---|---|
| native MbCNC1 | P21 | 7.0 | 1.9 | closed | 0.84 | 2.4 | >4.0 | in | 0.86 | 0.65 |
| native MbCNC2 | P21 | 5.6 | 1.7 | open | 0.53 | >4.0 | 2.6 | in | 0.89 | 0.83 |
| native MbCNC2 | P21 | 7.0 | 2.0 | closed | 0.79 | 2.6 | >4.0 | in | 1.00 | 0.85 |
| native MbCNC3 | P21 | 7.0 | 1.8 | closed / open | 0.26 / 0.68 | 3.4 (closed) | 2.7 (open) | in / out | 0.33 / 0.69 | 0.71 |
| native MbCNC4 | P21 | 7.0 | 1.7 | open | 0.53 | >4.0 | 2.7 | out | 0.70 | 0.44 |
| native MbCNC4 | P21 | 9.0 | 2.0 | closed | 1.00 | 3.0 | >4.0 | in | 0.54 | 0.45 |
| wt MbCNC1 | P6 | 9.0 | 1.8 | closed | 1.00 | 2.9 | >4.0 | in | 0.80 | 0.60d |
| wt MbCNC2 | P6 | 9.0 | 1.8 | closed | 1.00 | 3.2 | >4.0 | in | 0.84 | 0.82d |
| wt MbCNC3 | P6 | 9.0 | 2.3 | closed | 1.00 | 3.0 | >4.0 | in | 0.68 | 0.69d |
| wt MbCNC4 | P6 | 9.0 | 1.9 | closed | 1.00 | 2.8 | >4.0 | in | 0.51 | 0.47d |
| F46V MbCNC4 | P6 | 9.0 | 2.1 | open | 1.00 | >4.0 | 3.7f | out | 0.68 | 0.26d |
| H64A MbCNC4 | P6 | 9.0 | 2.1 | NA | NA | NA | NA | out | 0.62 | NA |
| V68F MbCNC4 | P6 | 7.0 | 2.7 | closed / open | 0.45 / 0.53 | 2.7 (closed) | 3.1 (open) | in / out | 0.45 / 0.53 | 0.61 |
| V68F MbCNC4 | P6 | 9.0 | 2.1 | closed | 1.00 | 2.9 | >4.0 | in | 0.61 | 0.59 |
a
Occupancies are for the His64 imidazole.
b
Occupancies are for the CNR alkyl chain.
c
Solution based measurement. The fraction of complexes in the in conformation, Fin = (in peak Abs)/(in peak Abs + out peak Abs) (56).
d
Measured at pH 7.0.
e Although His64 occupies the open conformation, this distance is larger than expected due to rotation about its χ2 dihedral angle away from Asp60 to fill the vacant space left by the F46V mutation.