Helicase, superfamily 1, UvrD-related <p>Helicases have been classified in 5 superfamilies (SF1-SF5). All of theproteins bind ATP and, consequently, all of them carry the classical Walker A(phosphate-binding loop or P-loop) and Walker B(Mg2+-binding aspartic acid) motifs. For the two largest groups, commonlyreferred to as SF1 and SF2, a total of seven characteristic motifs have beenidentified [<cite idref="PUB00004361"/>] which are distributed over two structural domains, anN-terminal ATP-binding domain and a C-terminal domain. UvrD-like DNA helicasesbelong to SF1, but they differ from classical SF1/SF2 (see <db_xref db="INTERPRO" dbkey="IPR014021"/>) by alarge insertion in each domain. UvrD-like DNA helicases unwind DNA with a3'-5' polarity [<cite idref="PUB00033615"/>].</p><p>Crystal structures of several uvrD-like DNA helicases have been solved [<cite idref="PUB00000949"/>, <cite idref="PUB00032879"/>, <cite idref="PUB00033616"/>]. They are monomeric enzymes consisting of twodomains with a common alpha-beta RecA-like core. The ATP-binding site issituated in a cleft between the N terminus of the ATP-binding domain and thebeginning of the C-terminal domain. The enzyme crystallizes in two differentconformations (open and closed). The conformational difference between the twoforms comprises a large rotation of the end of the C-terminal domain byapproximately 130 degrees. This "domain swiveling" was proposed to be an importantaspect of the mechanism of the enzyme [<cite idref="PUB00032879"/>].</p><p>Some proteins that belong to the UvrD-like DNA helicase family are listedbelow:<ul> <li>Bacterial UvrD helicase. It is involved in the post-incision events of nucleotide excision repair and methyl-directed mismatch repair. It unwinds DNA duplexes with 3'-5' polarity with respect to the bound strand and initiates unwinding most effectively when a single-stranded region is present.</li> <li>Gram-positive bacterial pcrA helicase, an essential enzyme involved in DNA repair and rolling circle replication. The <taxon tax_id="1280">Staphylococcus aureus</taxon> pcrA helicase has both 5'-3' and 3'-5' helicase activities.</li> <li>Bacterial rep proteins, a single-stranded DNA-dependent ATPase involved in DNA replication which can initiate unwinding at a nick in the DNA. It binds to the single-stranded DNA and acts in a progressive fashion along the DNA in the 3' to 5' direction.</li> <li>Bacterial helicase IV (helD gene product). It catalyzes the unwinding of duplex DNA in the 3'-5' direction.</li> <li>Bacterial recB protein. RecBCD is a multi-functional enzyme complex that processes DNA ends resulting from a double-strand break. RecB is a helicase with a 3'-5' directionality.</li> <li>Fungal srs2 proteins, an ATP-dependent DNA helicase involved in DNA repair. The polarity of the helicase activity was determined to be 3'-5'.</li></ul></p><p>This entry represents the ATP-binding domain found in UvrD-like helicases.</p>