Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:6.1.1.18 (glutaminyl-tRNA synthetase)
 231 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The structure of the mammalian multi-synthetase complex was investigated in vitro using qualitative and quantitative approaches. This macromolecular assemblage comprises the bifunctional glutamyl-prolyl-tRNA synthetase, the seven monospecific isoleucyl, leucyl, methionyl, glutaminyl, lysyl, arginyl and aspartyl-tRNA synthetases, and the three auxiliary p43, p38 and p18 proteins. The scaffold p38 protein was expressed in Escherichia coli and purified to homogeneity as a His-tagged protein. The different components of the complex were shown to associate in vitro with p38 immobilized on Ni(2+)-coated plates. Interactions between peripheral enzymes and p38 are referred to as central interactions, as opposed to lateral interactions between peripheral enzymes. Kinetic parameters of the interactions were determined by the means of a biosensor-based approach. The two dimeric proteins LysRS and AspRS were found to tightly bind to p38, with a K(d) value of 0.3 and 4.7 nM, respectively. These interactions involved the catalytic core of the enzymes. By contrast, binding of ArgRS or GlnRS to p38 was much weaker (>5 microM). ArgRS and p43, two peripheral components, were shown to interact with moderate affinity (K(d)=93 nM). Since all the components of the complex are tightly associated within this particle, lateral interactions were believed to contribute to the stabilization of this assemblage. Using an in vitro binding assay, concomitant association of several components of the complex on immobilized p38 could be demonstrated, and revealed the involvement of synergistic effects for association of weakly interacting proteins. Taking into account the possible synergy between central and lateral contributions, a sub-complex containing p38, p43, ArgRS and GlnRS was reconstituted in vitro. These data provide compelling evidence for an ordered and concerted mechanism of complex assembly.
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PMID:Macromolecular assemblage of aminoacyl-tRNA synthetases: quantitative analysis of protein-protein interactions and mechanism of complex assembly. 1112 41

When compared to other conserved housekeeping protein families, such as ribosomal proteins, during the evolution of higher eukaryotes, aminoacyl-tRNA synthetases (aaRSs) show an apparent high propensity to add new sequences, and especially new domains. The stepwise emergence of those new domains is consistent with their involvement in a broad range of biological functions beyond protein synthesis, and correlates with the increasing biological complexity of higher organisms. These new domains have been extensively characterized based on their evolutionary origins and their sequence, structural, and functional features. While some of the domains are uniquely found in aaRSs and may have originated from nucleic acid binding motifs, others are common domain modules mediating protein-protein interactions that play a critical role in the assembly of the multi-synthetase complex (MSC). Interestingly, the MSC has emerged from a miniature complex in yeast to a large stable complex in humans. The human MSC consists of nine aaRSs (LysRS, ArgRS, GlnRS, AspRS, MetRS, IleRS, LeuRS, GluProRS, and bifunctional aaRs) and three scaffold proteins (AIMP1/p43, AIMP2/p38, and AIMP3/p18), and has a molecular weight of 1.5 million Dalton. The MSC has been proposed to have a functional dualism: facilitating protein synthesis and serving as a reservoir of non-canonical functions associated with its synthetase and non-synthetase components. Importantly, domain additions and functional expansions are not limited to the components of the MSC and are found in almost all aaRS proteins. From a structural perspective, multi-functionalities are represented by multiple conformational states. In fact, alternative conformations of aaRSs have been generated by various mechanisms from proteolysis to alternative splicing and posttranslational modifications, as well as by disease-causing mutations. Therefore, the metamorphosis between different conformational states is connected to the activation and regulation of the novel functions of aaRSs in higher eukaryotes.
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PMID:Architecture and metamorphosis. 2353 45