Crystal structure of tetrameric form of human lysyl-tRNA synthetase: Implications for multisynthetase complex formation

Abstract

In mammals, many aminoacyl-tRNA synthetases are bound together in a multisynthetase complex (MSC) as a reservoir of procytokines and regulation molecules for functions beyond aminoacylation. The ␣2 homodimeric lysyl-tRNA synthetase (LysRS) is tightly bound in the MSC and, under specific conditions, is secreted to trigger a proinflammatory response. Results by others suggest that ␣2 LysRS is tightly bound into the core of the MSC with homodimeric ␤2 p38, a scaffolding protein that itself is multifunctional. Not understood is how the two dimeric proteins combine to make a presumptive ␣2␤2 heterotetramer and, in particular, the location of the surfaces on LysRS that would accommodate the p38 interactions. Here we present a 2.3-Å crystal structure of a tetrameric form of human LysRS. The relatively loose (as seen in solution) tetramer interface is assembled from two eukaryotespecific sequences, one in the catalytic-and another in the anticodon-binding domain. This same interface is predicted to provide unique determinants for interaction with p38. The analyses suggest how the core of the MSC is assembled and, more generally, that interactions and functions of synthetases can be built and regulated through dynamic protein-protein interfaces. These interfaces are created from small adaptations to what is otherwise a highly conserved (through evolution) polypeptide sequence.AIMP2 ͉ aminoacyl-tRNA synthetase ͉ p38

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

“…These mutations were also effective in disrupting the dimeric interface of the protein, which was evident by DLS measurements and reduced aminoacylation activity. HIV-1 Gag and hLysRS are both capable of homodimer formation, as well as higher order oligomerization (14,29). However, previous work showed that homodimerization of these proteins is not important for their interaction, because a monomeric triple mutant variant still bound with an affinity within 2-fold of that of WT LysRS (21).…”

“…The published crystal structure (Protein Data Bank code 3bju) of LysRS (14) was first used to measure the largest end to end distance of the dimeric (ϳ10.7 nm) and monomeric (ϳ8.5 nm) proteins (Fig. 4B, inset).…”

“…Class II synthetases are generally functional dimers or tetramers, and their active sites consist of an antiparallel ␤-sheet structure and three highly degenerate con-* This work was supported, in whole or in part, by National Institutes of Health sensus sequences (motifs 1, 2, and 3). Motif 1, which is comprised of ␣-helices 5, 6, and 7 (H7) and part of a ␤-sheet (␤6), constitutes the dimer interface, whereas motif 2 and 3 together constitute the aminoacylation active site (12)(13)(14). Although an ␣ 2 homodimer is the functional oligomerization state for aminoacylation, hLysRS crystallized as an ␣ 2 ␣ 2 tetramer (14).…”

“…Motif 1, which is comprised of ␣-helices 5, 6, and 7 (H7) and part of a ␤-sheet (␤6), constitutes the dimer interface, whereas motif 2 and 3 together constitute the aminoacylation active site (12)(13)(14). Although an ␣ 2 homodimer is the functional oligomerization state for aminoacylation, hLysRS crystallized as an ␣ 2 ␣ 2 tetramer (14). LysRS is also part of the high molecular weight multisynthetase complex (MSC) present in higher eukaryotes (15).…”

Anticodon-like binding of the HIV-1 tRNA-like element to human lysyl-tRNA synthetase

“…Blue residues are those that are affected by ACSL and WT TLE but not U9. The protein structure was generated using the hLysRS ACB domain coordinates (Guo et al 2008) and rendered using a protein surface.…”