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Literature summary for 3.6.5.4 extracted from
- Structure and switch cycle of SRbeta as ancestral eukaryotic GTPase associated with secretory membranes (2015), Structure, 23, 1838-1847 .
Cloned(Commentary)
| Cloned (Comment) | Organism |
|---|---|
| gene CTHT_0050420, sequence comparisons | Thermochaetoides thermophila |
Crystallization (Commentary)
| Crystallization (Comment) | Organism |
|---|---|
| purified recombinant SRbeta in complex with the SRX domain of SRalpha in the GTP-bound state and of GDP- and GDP-Mg2+-bound SRbeta, X-ray diffraction structure determination and analysis at 1.9-3.2 A resolution | Thermochaetoides thermophila |
Localization
| Localization | Comment | Organism | GeneOntology No. | Textmining |
|---|---|---|---|---|
| endoplasmic reticulum membrane | - |
Thermochaetoides thermophila | 5789 | - |
| membrane | SRbeta is an integral membrane component of the signal recognition particle (SRP) receptor | Thermochaetoides thermophila | 16020 | - |
| ribosome | the SRbeta-ribosome interaction relies on SRalpha, when SRbeta is in the GTP-bound state | Thermochaetoides thermophila | 5840 | - |
Metals/Ions
| Metals/Ions | Comment | Organism | Structure |
|---|---|---|---|
| Mg2+ | required, residues Thr64 and Ser107 are directly involved in magnesium coordination | Thermochaetoides thermophila |  |
Natural Substrates/ Products (Substrates)
| Natural Substrates | Organism | Comment (Nat. Sub.) | Natural Products | Comment (Nat. Pro.) | Rev. | Reac. |
|---|---|---|---|---|---|---|
| GTP + H2O | Thermochaetoides thermophila | - |
GDP + phosphate | - |
? | |
| GTP + H2O | Thermochaetoides thermophila IMI 039719 | - |
GDP + phosphate | - |
? | |
| GTP + H2O | Thermochaetoides thermophila DSM 1495 | - |
GDP + phosphate | - |
? | |
| GTP + H2O | Thermochaetoides thermophila CBS 144.50 | - |
GDP + phosphate | - |
? | |
Organism
| Organism | UniProt | Comment | Textmining |
|---|---|---|---|
| Thermochaetoides thermophila | G0SD15 | signal recognition particle 54 kDa protein subunit with GTPase activity | - |
| Thermochaetoides thermophila CBS 144.50 | G0SD15 | signal recognition particle 54 kDa protein subunit with GTPase activity | - |
| Thermochaetoides thermophila DSM 1495 | G0SD15 | signal recognition particle 54 kDa protein subunit with GTPase activity | - |
| Thermochaetoides thermophila IMI 039719 | G0SD15 | signal recognition particle 54 kDa protein subunit with GTPase activity | - |
Substrates and Products (Substrate)
| Substrates | Comment Substrates | Organism | Products | Comment (Products) | Rev. | Reac. |
|---|---|---|---|---|---|---|
| GTP + H2O | - |
Thermochaetoides thermophila | GDP + phosphate | - |
? | |
| GTP + H2O | - |
Thermochaetoides thermophila IMI 039719 | GDP + phosphate | - |
? | |
| GTP + H2O | - |
Thermochaetoides thermophila DSM 1495 | GDP + phosphate | - |
? | |
| GTP + H2O | - |
Thermochaetoides thermophila CBS 144.50 | GDP + phosphate | - |
? | |
| additional information | both SRalpha and SRbeta are GTPases | Thermochaetoides thermophila | ? | - |
- |
|
| additional information | both SRalpha and SRbeta are GTPases | Thermochaetoides thermophila IMI 039719 | ? | - |
- |
|
| additional information | both SRalpha and SRbeta are GTPases | Thermochaetoides thermophila DSM 1495 | ? | - |
- |
|
| additional information | both SRalpha and SRbeta are GTPases | Thermochaetoides thermophila CBS 144.50 | ? | - |
- |
|
Subunits
| Subunits | Comment | Organism |
|---|---|---|
| heterodimer | SRP GTPases are multi-domain proteins. SRalpha consists of an N-terminal SNARE-like Longin domain (SRX domain) that is connected by a long flexible linker to the NG domain, which harbors the GTPase activity. The SRX domain is responsible for interaction with the SRbeta GTPase in a GTP-dependent manner | Thermochaetoides thermophila |
| monomer | SRbeta is a small monomeric GTPase | Thermochaetoides thermophila |
Synonyms
| Synonyms | Comment | Organism |
|---|---|---|
| CtSR | - |
Thermochaetoides thermophila |
| SRbeta GTPase | - |
Thermochaetoides thermophila |
| SRP GTPase | - |
Thermochaetoides thermophila |
General Information
| General Information | Comment | Organism |
|---|---|---|
| evolution | the signal recognition particle receptor SRbeta belongs to the Ras-family of small monomeric GTPases, specific differences to the Arf and Sar1 families with implications for GTPase regulation are determined, overview. SRbeta is the oldest member of all small GTPases branching first in eukaryotic evolution | Thermochaetoides thermophila |
| additional information | the structures of the SRbeta-GTPase in its GTP- and GDP-states describe a switch cycle revealing a fixed switch II region. The linker region between the N-terminal SRX domain and the C-terminal NG domain of SRalpha is crucial for ribosome binding of the SR. Analysis of the structure of the ctSRbeta-GTP/SRX complex and of ctSRbeta-GDP complex, overview. The conformation of SRbeta does not directly influence ribosome binding but rather regulates the SRX interaction during the switch cycle. ctSRbeta contains all consensus fingerprints that define the SRbeta family, which like for all GTPases cluster around the nucleotide. The fingerprints are GxxxxGKS/T64 for the P loop, TxxS107 within the switch I region (residues 99-110), DxPGHxxLR154 within the switch II region (residues 146-160), and NKxD253 for the guanine binding pocket. The catalytic residue His150 is in a resting position pointing outward of the active center, rendering the ctSRbeta-GTP/SRX complex inactive. The histidine is tied to the backbone nitrogen of Lys152 within switch II and therefore it must be available in the deprotonated form. A unique feature of SRbeta applies to the switch II fingerprint. The conserved fingerprint within Arf and Sar1 writes as DxGG(QArf/HSar1)xxxRxW, and this signature is the prerequisite for the family-specific interswitch toggle mechanism. While most of the fingerprint is conserved in the SRb family, the first glycine is replaced by the rigid proline and the terminal tryptophan is not present. CtSRX not only contacts switch I, but also interacts with the N-terminal turn of helix alpga2 (HxxL153) in the switch II region. Most importantly, the C-terminal Pi-helical turn of helix alpha1x (X1xxFFX2) sequesters the catalytic histidine His150 away from the active center | Thermochaetoides thermophila |
| physiological function | the signal recognition particle receptor (SR) targets nascent protein chains to the endoplasmic reticulum. The eukaryotic SR consists of the two GTPases SRalpha and SRbeta. SRbeta-GTP interacts with ribosomes only in presence of SRalpha | Thermochaetoides thermophila |
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