Nature of the Interface Bonding
Frequency of Salt Bridges
The right-skew of the histogram shows the unlikelihood of finding salt bridges (>2) at protein-protein interfaces.
The number of salt bridges at interfaces IML3:CHL4 (L:N) and MCM16:CHL4 (H:N) fall within the peak as predicted.
Interface CHL4:CTF19 (N:P) falls within the low frequency range of salt bridges.
Most interestingly, interface CHL4:MCM21 (N:O) contains 10 salt bridges - an uncommon occurrence. This could probably be accounted for by its large and uncommon BSA.
Frequency of Hydrogen Bonds
Similar to the histogram for salt bridge frequency, this histogram shows a right-skew.
Interfaces CHL4:MCM21 (N:O) and CHL4:CTF19 (N:P) fall within the peak number of hydrogen bonds, whilst interface IML3:CHL4 (L:N) is slightly to the right of the peak, indicating a lower frequency of hydrogen bonds.
Frequency of Van der Waals' forces
The right-skewed histogram shows that all the major interfaces of the CHL4 C-terminal domain fall within the peak.
Contrary to the other interfaces, minor interface MCM16:CHL4 (H:N) has a significant small number of Van der Waals' (non-bonded) interactions.