8UCZ

Sterile Alpha Motif (SAM) domain from Tric1 from Arabidopsis thaliana - D235A mutant

Summary for 8UCZ

• Entry DOI: 10.2210/pdb8ucz/pdb
• Descriptor: Chloroplastic import inner membrane translocase subunit HP30-1, CHLORIDE ION (3 entities in total)
• Functional Keywords: mitochondria, trna import, tric1, sam domain, oligomerization, prat domain, sterile alpha motif domain, rna binding protein
• Biological source: Arabidopsis thaliana (thale cress)
• Total number of polymer chains: 3
• Total formula weight: 30471.68

Authors

Olasz, B.,Vrielink, A.,Smithers, L. (deposition date: 2023-09-27, release date: 2024-05-01, Last modification date: 2024-05-15)

Primary citation

Olasz, B.,Smithers, L.,Evans, G.L.,Anandan, A.,Murcha, M.W.,Vrielink, A.
Structural analysis of the SAM domain of the Arabidopsis mitochondrial tRNA import receptor.
J.Biol.Chem., 300:107258-107258, 2024

PubMed Abstract: Mitochondria are membrane bound organelles of endosymbiotic origin with limited protein coding capacity. The import of nuclear-encoded protein and nucleic acids is required and essential for maintaining organelle mass, number and activity. As plant mitochondria do not encode all the necessary tRNA types required, the import of cytosolic tRNA is vital for organelle maintenance. Recently, two mitochondrial outer membrane proteins, named Tric1 and Tric2, for tRNA import component, were shown to be involved in the import of cytosolic tRNA. Tric1/2 binds tRNA via conserved residues in the C-terminal Sterile Alpha Motif (SAM) domain. Here we report the X-ray crystal structure of the Tric1 SAM domain. We identified the ability of the SAM domain to form a helical superstructure with 6 monomers per helical turn and key amino acid residues responsible for its formation. We determined that the oligomerization of Tric1 SAM domain may play a role in protein function whereby mutation of Gly241 introducing a larger side chain at this position disrupted the oligomer and resulted in the loss of RNA binding capability. Furthermore, complementation of Arabidopsis thaliana Tric1/2 knockout lines with a mutated Tric1 failed to restore the defective plant phenotype. AlphaFold2 structure prediction of both the SAM domain and Tric1 support a cyclic pentameric or hexameric structure. In the case of a hexameric structure a pore of sufficient dimensions to transfer tRNA across the mitochondrial membrane is observed. Our results highlight the importance of oligomerization of Tric1 for protein function.

PubMed: 38582448
DOI: 10.1016/j.jbc.2024.107258

Experimental method

X-RAY DIFFRACTION (2.07 Å)