Table 2

Subunit interactions.

Subunit interfaceBuried surface area (Å2)*Salt bridgesHydrogen bondsβ-addition motifs§
Rpb1-Rpb217,178658Rpb2-β41-Rpb1-β7; Rpb2-β45-Rpb1-β1
Rpb1-Rpb360813-
Rpb1-Rpb54,768519-
Rpb1-Rpb63,797312Rpb1-β35-Rpb6-β3
Rpb1-Rpb83,05636Rpb8-β6-Rpb1-β18
Rpb1-Rpb93,011221Rpb9-β4-Rpb1-β28
Rpb1-Rpb111,913-8-
Rpb2-Rpb33,070526-
Rpb2-Rpb92,70515-
Rpb2-Rpb102,941111-
Rpb2-Rpb1160812-
Rpb2-Rpb121,923414Rpb12-β3-Rpb2-β32
Rpb3-Rpb833311-
Rpb3-Rpb102,175415-
Rpb3-Rpb113,89946-
Rpb3-Rpb1299337Rpb12-β4-Rpb3-β3
Rpb5-Rpb620413-
Rpb8-Rpb11396---
Total53,578452177 instances
  • * Calculated with programs AREAIMOL and RESAREA (73) with a standard probe radius of 1.4 Å.

  • A conservative distance cut-off of 3.6 Å was used [program CONTACT (73)].

  • Potential hydrogen bonds with a donor-acceptor distance below 3.3 Å were included.

  • § The order of strands in a β-addition motif is added β strand–accepting strand of a β sheet. Biochemical mapping (80) suggests that the β-addition motif formed by Rpb1 and Rpb9 may be largely responsible for the interaction of these subunits. The β-addition motif formed between Rpb1 and Rpb6 restrains clamp mobility.