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Expression and analysis of the SAM-dependent RNA methyltransferase Rsm22 from Saccharomyces cerevisiae

DOI: 10.1107/S2059798321004149 DOI Help

Authors: Jahangir Alam (University of Oulu) , Farah Tazkera Rahman (University of Oulu) , Shiv Sah-Teli (University of Oulu) , Rajaram Venkatesan (University of Oulu) , M. Kristian Koski (Biocenter Oulu) , Kaija J. Autio (University of Oulu) , J. Kalervo Hiltunen (University of Oulu) , Alexander J. Kastaniotis (University of Oulu)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Acta Crystallographica Section D Structural Biology , VOL 77

State: Published (Approved)
Published: June 2021
Diamond Proposal Number(s): 14794

Open Access Open Access

Abstract: The Saccharomyces cerevisiae Rsm22 protein (Sc-Rsm22), encoded by the nuclear RSM22 (systematic name YKL155c) gene, is a distant homologue of Rsm22 from Trypanosoma brucei (Tb-Rsm22) and METTL17 from mouse (Mm-METTL17). All three proteins have been shown to be associated with mitochondrial gene expression, and Sc-Rsm22 has been documented to be essential for mitochondrial respiration. The Sc-Rsm22 protein comprises a polypeptide of molecular weight 72.2 kDa that is predicted to harbor an N-terminal mitochondrial targeting sequence. The precise physiological function of Rsm22-family proteins is unknown, and no structural information has been available for Sc-Rsm22 to date. In this study, Sc-Rsm22 was expressed and purified in monomeric and dimeric forms, their folding was confirmed by circular-dichroism analyses and their low-resolution structures were determined using a small-angle X-ray scattering (SAXS) approach. The solution structure of the monomeric form of Sc-Rsm22 revealed an elongated three-domain arrangement, which differs from the shape of Tb-Rsm22 in its complex with the mitochondrial small ribosomal subunit in T. brucei (PDB entry 6sg9). A bioinformatic analysis revealed that the core domain in the middle (Leu117–Asp462 in Sc-Rsm22) resembles the corresponding region in Tb-Rsm22, including a Rossmann-like methyltransferase fold followed by a zinc-finger-like structure. The latter structure is not present in this position in other methyltransferases and is therefore a unique structural motif for this family. The first half of the C-terminal domain is likely to form an OB-fold, which is typically found in RNA-binding proteins and is also seen in the Tb-Rsm22 structure. In contrast, the N-terminal domain of Sc-Rsm22 is predicted to be fully α-helical and shares no sequence similarity with other family members. Functional studies demonstrated that the monomeric variant of Sc-Rsm22 methylates mitochondrial tRNAs in vitro. These data suggest that Sc-Rsm22 is a new and unique member of the RNA methyltransferases that is important for mitochondrial protein synthesis.

Journal Keywords: mitochondrial ribosomes; methyltransferases; Rsm22; crystallization; SAXS structure

Diamond Keywords: Enzymes

Subject Areas: Biology and Bio-materials, Chemistry

Instruments: B21-High Throughput SAXS

Added On: 25/05/2021 11:47


Discipline Tags:

Biochemistry Chemistry Structural biology Life Sciences & Biotech

Technical Tags:

Scattering Small Angle X-ray Scattering (SAXS)