<p>This entry represents an alpha-helical bundle domain, which has a SAM domain-like fold. This compact domain consists of a 4-5 helical bundle of two orthogonally packed alpha-hairpins, and contains one classic and one pseudo HhH (helix-hairpin-helix) motif. This domain is found at N-terminal of the DNA repair protein Rad1, at the C-terminal of the transcription elongation protein NusA, and at the C-terminal of the hypothetical protein AF1548.</p><p> Human Rad51 protein is a homologue of <taxon tax_id="562">Escherichia coli</taxon> RecA protein, and functions in DNA repair and recombination [<cite idref="PUB00014057"/>]. In higher eukaryotes, Rad51 protein is essential for cell viability. The N-terminal region of Rad51 is highly conserved among eukaryotic Rad51 proteins but is absent from RecA, suggesting a Rad51-specific function for this region. The-terminal domain is involved in interactions with DNA and proteins; DNA binding may be regulated via phosphorylation within the N-terminal domain.</p><p>NusA (N utilisation substance A) from E. coli is an essential transcription factor that associates with the RNA polymerase (RNAP) core enzyme, where it modulates transcriptional pausing, termination and anti-termination [<cite idref="PUB00035974"/>]. The C-terminal of NusA consists of two repeat units, and is responsible for the interaction of NisA with the C-terminal of RNAP, and with its interaction with protein N from phage lambda during anti-termination [<cite idref="PUB00031711"/>].</p>