Refinement statistics.

#Rfactor = Σ ||Fobs| - |Fcalc||/Σ | Fobs|. *Rfree was calculated with 5% of reflections excluded from the whole refinement procedure. $G factor is an overall measure of structure quality from PROCHECK [41]. The numbers in parentheses refers to the last (highest) resolution shell. ∧Bound (“B”) monomers and free (“F”) monomers were tightly restrained as two separate groups. +Mean B-factors are shown after TLS refinement. Mean B-factors without TLS refinement are given in parenthesis for comparison.