<p>This entry represents a domain with a winged helix-type fold, which consists of a closed 3-helical bundle with a right-handed twist, and a small beta-sheet wing [<cite idref="PUB00022119"/>]. Different winged helix domains share a common structure, but can differ in sequence. This entry is designated "type 3". </p><p>The winged helix motif is involved in both DNA and RNA binding. In the elongation factor SelB, the winged helix domains recognise RNA, allowing the complex to wrap around the small ribosomal subunit. In bacteria, the incorporation of the amino acid selenocysteine into proteins requires elongation factor SelB, which binds both transfer RNA (tRNA) and mRNA. SelB binds to an mRNA hairpin formed by the selenocysteine insertion sequence (SECIS) with extremely high specificity [<cite idref="PUB00033963"/>]. </p>