2.1 | Defining evaluation units
Domains are basic folding units of proteins. They can be mobile, and
their relative position can deviate depending on environmental
conditions (e.g., the presence of a ligand), protein’s functional state
(e.g., open or closed) or structure determination factors (e.g., crystal
packing). Thus, evaluating models versus a specific domain conformation
in a multi-domain structure can be too restrictive and penalizing. To
address this issue, CASP adopted a domain-based approach to evaluating
models, where multidomain targets are first split into smaller
evaluation units. Even though the recent progress in modeling and the
availability of non-rigid body structure comparison methods make
splitting of targets into EUs less critical, we kept this practice to
allow fair comparison of results across CASPs. A detailed procedure is
described below.