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Literature summary for 3.6.4.B8 extracted from
- Structure of the active form of human origin recognition complex and its ATPase motor module (2017), eLife, 6, e20818 .
Crystallization (Commentary)
| Crystallization (Comment) | Organism |
|---|---|
| purified recombinant ORC in active form, X-ray diffraction structure determination and analysis at 3.39 A resolution, molecular replacement using the Drosophila melanogaster DmORC4, DmORC5-AAA+ domain and DmORC1-WHD of the DmORC complex as template | Homo sapiens |
Protein Variants
| Protein Variants | Comment | Organism |
|---|---|---|
| D125A | site-directed mutagenesis of subunit ORC5 at the ATP-binding site | Homo sapiens |
| D159A | site-directed mutagenesis of subunit ORC4 at the ATP-binding site. The mutation of the ORC4 Walker-B motif has little effect on ATPase activity | Homo sapiens |
| D620A | site-directed mutagenesis of subunit ORC1 at the ATP-binding site. Disrupting the ORC1 Walker-B motif effectively abolishes ATPase activity | Homo sapiens |
| D620A/D159A | site-directed mutagenesis of subunits ORC1 and ORC4 at the ATP-binding site. The double mutation of the Walker-B motif of both ORC1 and ORC4 abolishes activity | Homo sapiens |
| R261Q | site-directed mutagenesis of subunit ORC3 at the ATP-binding site | Homo sapiens |
| R69V | site-directed mutagenesis of subunit ORC4 at the ATP-binding site | Homo sapiens |
| R720Q | site-directed mutagenesis of subunit ORC1 at the ATP-binding site. The mutation abolishes ATPase activity of the motor module, and this mutation exists in a single heterozygous individual with a wild-type allele | Homo sapiens |
| R98Q | site-directed mutagenesis of subunit ORC3 at the ATP-binding site | Homo sapiens |
| Y174C | site-directed mutagenesis of subunit ORC4 at the ATP-binding site. The ORC4-Y174C mutation in the ORC4 tether, which disrupts its hydrogen bond to an ORC1 Walker-B side chain (ORC1-E621), renders the motor module hyperactive for ATPase activity. The ORC4 MGS mutant Y174C has reduced activity (at about 50% of wild-type) in the context of ORC1-5. The hyperactivity of this mutant observed in the context of the motor module alone suggests that binding of ORC2-ORC3 modulates the ATPase activity of the ORC motor | Homo sapiens |
Localization
| Localization | Comment | Organism | GeneOntology No. | Textmining |
|---|---|---|---|---|
| nucleus | - |
Homo sapiens | 5634 | - |
Metals/Ions
| Metals/Ions | Comment | Organism | Structure |
|---|---|---|---|
| Mg2+ | required | Homo sapiens |  |
Natural Substrates/ Products (Substrates)
| Natural Substrates | Organism | Comment (Nat. Sub.) | Natural Products | Comment (Nat. Pro.) | Rev. | Reac. |
|---|---|---|---|---|---|---|
| ATP + H2O | Homo sapiens | - |
ADP + phosphate | - |
? | |
Organism
| Organism | UniProt | Comment | Textmining |
|---|---|---|---|
| Homo sapiens | Q13415 AND Q13416 AND Q9UBD5 AND O43929 AND O43913 AND Q9Y5N6 | genes encoding subunits ORC1-6 | - |
Substrates and Products (Substrate)
| Substrates | Comment Substrates | Organism | Products | Comment (Products) | Rev. | Reac. |
|---|---|---|---|---|---|---|
| ATP + H2O | - |
Homo sapiens | ADP + phosphate | - |
? | |
| additional information | the ORC motor module displays robust ATPase activity, which is independent of DNA binding, nucleotide-binding site analysis, overview. In the context of the motor module, only the ORC1/4 interface is a functional ATPase. The RecA-fold and lid domains of HsORC1 form a classic ATPase site | Homo sapiens | ? | - |
- |
|
Subunits
| Subunits | Comment | Organism |
|---|---|---|
| hexamer | the enzyme complex is organized as a double-layered shallow corkscrew, with the AAA+ and AAA+-like domains forming one layer, and the winged-helix domains (WHDs) forming a top layer. CDC6 fits easily between ORC1 and ORC2, completing the ring and the DNA-binding channel, forming an additional ATP hydrolysis site. The overall architecture of the HsORC motor module resembles a cashew nut. Each ORC subunit is comprised of three domains: the RecA-fold, the alpha-helical lid and the alpha-helical winged-helix domain (WHD), although the WHD domain is truncated in ORC5. The RecA-fold domain and the lid together constitute the well-known AAA+ domain. The three RecA domains form a semicircle with ATP nucleotides wedged between them in a classic AAA+ oligomerization arrangement. In the context of the motor module, only the ORC1/4 interface is a functional ATPase. SUbunit HsCDC6 binds to the core of HsORC as a second step in the assembly of the pre-RC. It is also an AAA+ ATPase with 29% sequence identity to ORC1, and completes the ring structure | Homo sapiens |
Synonyms
| Synonyms | Comment | Organism |
|---|---|---|
| ATPase | - |
Homo sapiens |
| ORC | - |
Homo sapiens |
| origin recognition complex | - |
Homo sapiens |
General Information
| General Information | Comment | Organism |
|---|---|---|
| evolution | the enzyme complex belongs to the AAA+ ATPase family. The complex is composed of an ORC1/4/5 motor module lobe in an organization reminiscent of the DNA polymerase clamp loader complexes. The structure of HsORC reveals a remarkable similarity between two very different ATPases: the replication initiator ORC-CDC6 ATPase and the replication fork DNA polymerase clamp loader. Both ATPases function at different times during genome replication but load ring-shaped proteins onto double-stranded DNA so that the ring-shaped proteins become topologically linked to the DNA double helix. The ATPase motor module of HsORC is very reminiscent of the DNA polymerase clamp loader complexes such as replication factor C (RFC) in eukaryotes, the bacterial gamma-complex, and the T4 bacteriophage Gene44 clamp loader | Homo sapiens |
| malfunction | ORC molecular defects are observed in Meier-Gorlin syndrome mutations | Homo sapiens |
| additional information | determination and analysis of the structure of human ORC (HsORC motor module) in a functionally active, ATP-hydrolysis ready state, providing insight into ATP-dependent protein loading as well as DNA and CDC6 binding, structure-function relationship, overview. In the context of the motor module, only the ORC1/4 interface is a functional ATPase. Binding of ORC2-ORC3 modulates the ATPase activity of the ORC motor | Homo sapiens |
| physiological function | the first step in genome replication, the binding of the origin recognition complex (ORC) at origins of DNA replication, triggers a series of highly coordinated steps leading to the assembly of pre-replicative complexes (pre-RCs) in a process that involves CDC6 binding to ORC. ORC and CDC6 then function as an ATP-dependent assembler that first recruits a ring-shaped MCM2-7 hexamer with bound Cdt1 to DNA, and then loads a second MCM2-7 hexamer in a head-to-head orientation, whereby this double hexamer is topologically linked to double-stranded DNA. The enzyme complex loads ring-shaped proteins onto double-stranded DNA so that the ring-shaped proteins become topologically linked to the DNA double helix | Homo sapiens |
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