OBElike

OBElike is a term used in molecular biology and structural bioinformatics to describe proteins or protein domains that resemble the OB-fold in three-dimensional structure, even when their amino acid sequences show little similarity to canonical OB-fold families. The designation emphasizes structural similarity over sequence similarity and is often applied to domains that form a compact beta-barrel topology and participate in nucleic acid binding or related ligand interactions.

Origin and usage of the term vary across studies. OBElike is not a formally codified superfamily in major protein databases, but it appears in comparative analyses and annotations to group proteins that deploy OB-fold–like architectures despite divergent sequences. In this sense, OBElike serves as a practical label for recognizing structural conservation that is not readily detectable by sequence-based methods alone.

Structural features commonly associated with OBelikes include a small to medium-sized domain domain containing a beta-barrel core and loops that can engage nucleic acids, oligosaccharides, or other ligands. OBElike domains occur across different life domains and can be found as single modules or as parts of multi-domain proteins. Their functional roles are diverse, ranging from nucleic acid binding and chaperone activity to participation in replication, repair, or RNA metabolism, depending on the biological context.

Detection and classification of OBelikes rely on structural comparison and profile-based methods. Tools that assess three-dimensional similarity (such as DALI) or hidden Markov model–based approaches (like HHPred) assist in identifying OBelike architecture when sequence signals are weak. Researchers use the concept to explore evolutionary relationships among OB-fold–containing proteins and to annotate structurally similar but sequence-dissimilar domains.

See also: OB-fold, OB-fold–containing proteins, single-stranded DNA-binding proteins.