Limits...
Neurodegenerative disease-associated mutants of a human mitochondrial aminoacyl-tRNA synthetase present individual molecular signatures.

Sauter C, Lorber B, Gaudry A, Karim L, Schwenzer H, Wien F, Roblin P, Florentz C, Sissler M - Sci Rep (2015)

Bottom Line: The effects of these mutations on the structure and function of the enzymes remain to be established.Mutations with mild effects on solubility occur in patients as allelic combinations whereas those with strong effects on solubility or on aminoacylation are necessarily associated with a partially functional allele.The fact that all mutations show individual molecular and cellular signatures and affect amino acids only conserved in mammals, points towards an alternative function besides aminoacylation.

View Article: PubMed Central - PubMed

Affiliation: Architecture et Réactivité de l'ARN, CNRS, Université de Strasbourg, IBMC, 15 rue René Descartes, 67084 STRASBOURG Cedex, France.

ABSTRACT
Mutations in human mitochondrial aminoacyl-tRNA synthetases are associated with a variety of neurodegenerative disorders. The effects of these mutations on the structure and function of the enzymes remain to be established. Here, we investigate six mutants of the aspartyl-tRNA synthetase correlated with leukoencephalopathies. Our integrated strategy, combining an ensemble of biochemical and biophysical approaches, reveals that mutants are diversely affected with respect to their solubility in cellular extracts and stability in solution, but not in architecture. Mutations with mild effects on solubility occur in patients as allelic combinations whereas those with strong effects on solubility or on aminoacylation are necessarily associated with a partially functional allele. The fact that all mutations show individual molecular and cellular signatures and affect amino acids only conserved in mammals, points towards an alternative function besides aminoacylation.

No MeSH data available.


Related in: MedlinePlus

Locations and chemical nature of the amino acid substitutions of LBSL-associated mutations within functional domains of mt-AspRS.(A) Schematic representation of the modular organization of the human mt-AspRS (adapted from23). Structural modules are the anticodon (AC) binding domain (dark grey), the hinge region (white), and the catalytic domain (light grey). –Insertion– and –Extension– stands for bacterial-type insertion (white) and C-terminal extension (black) domains, respectively. Numbers correspond to amino acid positions flanking the different domains. Pink boxes situate catalytic motifs 1, 2, and 3, specific from class II aaRSs48. (B) Stereo view of the crystal structure of mt-AspRS (PDBid: 4AH6) with the positions of the studied mutations highlighted by color spheres. Color code on one monomer is as in panel (A). The second monomer is shown in gold. All molecular representations were prepared with PyMOL (Schrödinger, Inc.).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4664897&req=5

f1: Locations and chemical nature of the amino acid substitutions of LBSL-associated mutations within functional domains of mt-AspRS.(A) Schematic representation of the modular organization of the human mt-AspRS (adapted from23). Structural modules are the anticodon (AC) binding domain (dark grey), the hinge region (white), and the catalytic domain (light grey). –Insertion– and –Extension– stands for bacterial-type insertion (white) and C-terminal extension (black) domains, respectively. Numbers correspond to amino acid positions flanking the different domains. Pink boxes situate catalytic motifs 1, 2, and 3, specific from class II aaRSs48. (B) Stereo view of the crystal structure of mt-AspRS (PDBid: 4AH6) with the positions of the studied mutations highlighted by color spheres. Color code on one monomer is as in panel (A). The second monomer is shown in gold. All molecular representations were prepared with PyMOL (Schrödinger, Inc.).

Mentions: We recently determined the X-ray structure of human mt-AspRS26. This class II homodimeric synthetase shares a common architecture with its bacterial homologs, but is more thermolabile and exhibits a higher plasticity for the binding of tRNA26. Based on this knowledge we selected six clinically relevant single point mutations (Fig. 1) located in the N-terminal anticodon-binding domain (R58G, T136S), in the catalytic domain (Q184K, R263Q) or in the C-terminal extension (L613F, L626Q). Phenotypes of corresponding patients are listed in Supplementary Table 1. Previous in vitro assays had shown that R263Q is the only mutation of these six that significantly impairs the aminoacylation property of recombinant protein23. To investigate if and how these mutations change the solubility, thermal stability and structure in solution of mt-AspRS, we applied an integrated strategy based on comparative biochemical and biophysical analyses. The implications of these observations are discussed in the context of LBSL clinical pictures.


Neurodegenerative disease-associated mutants of a human mitochondrial aminoacyl-tRNA synthetase present individual molecular signatures.

Sauter C, Lorber B, Gaudry A, Karim L, Schwenzer H, Wien F, Roblin P, Florentz C, Sissler M - Sci Rep (2015)

Locations and chemical nature of the amino acid substitutions of LBSL-associated mutations within functional domains of mt-AspRS.(A) Schematic representation of the modular organization of the human mt-AspRS (adapted from23). Structural modules are the anticodon (AC) binding domain (dark grey), the hinge region (white), and the catalytic domain (light grey). –Insertion– and –Extension– stands for bacterial-type insertion (white) and C-terminal extension (black) domains, respectively. Numbers correspond to amino acid positions flanking the different domains. Pink boxes situate catalytic motifs 1, 2, and 3, specific from class II aaRSs48. (B) Stereo view of the crystal structure of mt-AspRS (PDBid: 4AH6) with the positions of the studied mutations highlighted by color spheres. Color code on one monomer is as in panel (A). The second monomer is shown in gold. All molecular representations were prepared with PyMOL (Schrödinger, Inc.).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4664897&req=5

f1: Locations and chemical nature of the amino acid substitutions of LBSL-associated mutations within functional domains of mt-AspRS.(A) Schematic representation of the modular organization of the human mt-AspRS (adapted from23). Structural modules are the anticodon (AC) binding domain (dark grey), the hinge region (white), and the catalytic domain (light grey). –Insertion– and –Extension– stands for bacterial-type insertion (white) and C-terminal extension (black) domains, respectively. Numbers correspond to amino acid positions flanking the different domains. Pink boxes situate catalytic motifs 1, 2, and 3, specific from class II aaRSs48. (B) Stereo view of the crystal structure of mt-AspRS (PDBid: 4AH6) with the positions of the studied mutations highlighted by color spheres. Color code on one monomer is as in panel (A). The second monomer is shown in gold. All molecular representations were prepared with PyMOL (Schrödinger, Inc.).
Mentions: We recently determined the X-ray structure of human mt-AspRS26. This class II homodimeric synthetase shares a common architecture with its bacterial homologs, but is more thermolabile and exhibits a higher plasticity for the binding of tRNA26. Based on this knowledge we selected six clinically relevant single point mutations (Fig. 1) located in the N-terminal anticodon-binding domain (R58G, T136S), in the catalytic domain (Q184K, R263Q) or in the C-terminal extension (L613F, L626Q). Phenotypes of corresponding patients are listed in Supplementary Table 1. Previous in vitro assays had shown that R263Q is the only mutation of these six that significantly impairs the aminoacylation property of recombinant protein23. To investigate if and how these mutations change the solubility, thermal stability and structure in solution of mt-AspRS, we applied an integrated strategy based on comparative biochemical and biophysical analyses. The implications of these observations are discussed in the context of LBSL clinical pictures.

Bottom Line: The effects of these mutations on the structure and function of the enzymes remain to be established.Mutations with mild effects on solubility occur in patients as allelic combinations whereas those with strong effects on solubility or on aminoacylation are necessarily associated with a partially functional allele.The fact that all mutations show individual molecular and cellular signatures and affect amino acids only conserved in mammals, points towards an alternative function besides aminoacylation.

View Article: PubMed Central - PubMed

Affiliation: Architecture et Réactivité de l'ARN, CNRS, Université de Strasbourg, IBMC, 15 rue René Descartes, 67084 STRASBOURG Cedex, France.

ABSTRACT
Mutations in human mitochondrial aminoacyl-tRNA synthetases are associated with a variety of neurodegenerative disorders. The effects of these mutations on the structure and function of the enzymes remain to be established. Here, we investigate six mutants of the aspartyl-tRNA synthetase correlated with leukoencephalopathies. Our integrated strategy, combining an ensemble of biochemical and biophysical approaches, reveals that mutants are diversely affected with respect to their solubility in cellular extracts and stability in solution, but not in architecture. Mutations with mild effects on solubility occur in patients as allelic combinations whereas those with strong effects on solubility or on aminoacylation are necessarily associated with a partially functional allele. The fact that all mutations show individual molecular and cellular signatures and affect amino acids only conserved in mammals, points towards an alternative function besides aminoacylation.

No MeSH data available.


Related in: MedlinePlus