Structural context for mobilization of a human tRNA synthetase from its cytoplasmic complex

Abstract

Human lysyl-tRNA synthetase is bound to the multi-tRNA synthetase complex (MSC) that maintains and regulates the aminoacylation and nuclear functions of LysRS. The p38 scaffold protein binds LysRS to the MSC and, only with the appropriate cue, mobilizes LysRS for redirection to the nucleus to interact with the microphthalmia associated transcription factor (MITF). In recent work, an ðα 2 Þ 2 LysRS tetramer crystallized to yield a high-resolution structure and raised the question of how LysRS is arranged (dimer or tetramer) in the MSC to interact with p38. To understand the structural organization of the LysRS-p38 complex that regulates LysRS mobilization, we investigated the complex by use of small angle X-ray scattering and hydrogen-deuterium exchange with mass spectrometry in solution. The structure revealed a surprising α 2 β 1 ∶β 1 α 2 organization in which a dimeric p38 scaffold holds two LysRS α 2 dimers in a parallel configuration. Each of the N-terminal 48 residues of p38 binds one LysRS dimer and, in so doing, brings two copies of the LysRS dimer into the MSC. The results suggest that this unique geometry, which reconfigures the LysRS tetramer from α 2 ∶α 2 to α 2 β 1 ∶β 1 α 2 , is designed to control both retention and mobilization of LysRS from the MSC.noncanonical function | p38/AIMP2 | structural plasticity

HIV-1 Exploits a Dynamic Multi-aminoacyl-tRNA Synthetase Complex To Enhance Viral Replication

“…The phosphomimetic S207D LysRS mutant is unable to bind p38/AIMP2 or any component of the MSC (16), which would increase the pool of free LysRS. Additionally, S207D LysRS has been shown to trigger a more "open" conformation, resulting in abolition of aminoacylation but not tRNA binding capacity in vitro (16,43). Our data are consistent with these previous findings and also show that S207D LysRS still binds tRNA Lys3 as well as WT LysRS.…”

Chemical inhibition of prometastatic lysyl-tRNA synthetase–laminin receptor interaction

“…19a–c). The model of the KRS T52D mutant suggested that phosphorylation at T52 could open up the ABD-CD interface and disturb the binding pocket for AIMP2, the binding partner of KRS within MSC 14,24 , thereby releasing p-T52 KRS from MSC (Fig. 4a and Supplementary Fig.…”

“…A fusion protein of human AIMP2 1–48 with TRX (thioredoxin) was constructed as described previously 24 . The purified protein was then labeled with EZ-Link-NHS-PEG 12 -Biotin according to the vendor’s instructions (Thermo Scientific).…”

Dual Role for Motif 1 Residues of Human Lysyl-tRNA Synthetase in Dimerization and Packaging into HIV-1

“…An intriguing observation that highlights the dynamic nature of LysRS within the cell, is illustrated by its mobilization to the nucleus (37). In the MSC, LysRS interacts with the dimeric p38 protein in a unique ␣ 2 ␤ 1 :␤ 1 ␣ 2 geometry; which is designed to control both retention and mobilization of LysRS from the MSC (16). In response to an immunological challenge, specific phosphorylation of Ser-207 of hLysRS has been shown to result in release of LysRS from the MSC and enhanced diadenosine tetraphosphate synthesis.…”

“…LysRS is also part of the high molecular weight multisynthetase complex (MSC) present in higher eukaryotes (15). Within the MSC, LysRS specifically interacts with the scaffold protein p38/ AIMP2 and is present in a unique ␣ 2 ␤ 1 :␤ 1 ␣ 2 orientation, which is designed to control both retention and mobilization of LysRS from the MSC (16).…”