Table 1.
Amino-acid residues that comprise filament intersubunit contacts and discrete, filament-specific cation-binding sites
| Actin filament region | Residuesa | Neighbor subunit residues |
|---|---|---|
| DNase 1 binding loopb | 36–52 | |
| Lateral contactsb | 110–114, 263–273 | 39, 40, 173, 191–197, 202c |
| Longitudinal contactsb | 36–52 | 139, 140, 143, 166–169, 346, 351, 374 |
| Polymerization cation sited | 62, 63, 202–206, 208 | 285–288, 290 |
| Stiffness cation sited | 36–38, 49–54, 57, 58, 61, 64, 65 | 167 |
a
Italicized residues are common between intersubunit contacts and predicted discrete cation-binding sites.
b
Residues comprising the DNase I binding loop obtained from Holmes et al. (51). Contacts determined from actin filament models (50,53).
c
Two potential salt bridges may exist in the lateral intersubunit contacts: one between Glu270 and either Arg39 or Thr202, and another between Lys113 and Glu195.
d
These sites represent an exhaustive list of residues with at least one nonhydrogen atom within 7.0 Å of predicted bound cation positions (18).