proteinannotation

Protein annotation is the process of attaching descriptive information to protein sequences and proteins. It seeks to define what a protein does, where it operates in the cell, how it functions, and how it relates to other molecules. Annotation covers molecular function, biological process, cellular localization, structural features, domains and motifs, enzymatic activity, and involvement in pathways, along with post-translational modifications and interaction networks. In some databases and literature, the term proteinannotation is used to refer to this concept.

Most annotation is inferred from sequence similarity to characterized proteins (homology-based transfer), motif and domain detection (Pfam, InterPro, PROSITE), and available experimental data. Structural information from known proteins can refine function. Annotations are stored in public databases (e.g., UniProt, GenBank/RefSeq) and linked to ontologies such as Gene Ontology (GO) and, when applicable, EC numbers for enzymes.

Annotations may be manual (curated) or computationally generated, with evidence codes indicating reliability. Results are shared across genome and proteome resources and exported in formats such as GFF and GAF, with cross-references to UniProt IDs, PDB entries, and pathway databases like KEGG.

Quality control is a major concern, as automated annotations can propagate errors. Ongoing curation, standardized evidence, and community curation help maintain accuracy. Protein annotation supports functional genomics, comparative biology, and drug discovery by enabling interpretation of experimental data and integration into biological networks.