Conformational communication mediates the reset step in t6A biosynthesis.
Amit Luthra1, Naduni Paranagama1, William Swinehart2
1Department of Chemistry and Biochemistry, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182, USA.
Nucleic Acids Research
|May 23, 2019
Summary
The N6-threonylcarbamoyladenosine (t6A) modification is vital for accurate protein synthesis. This study reveals the structure and mechanism of the bacterial TC-transfer complex, essential for t6A biosynthesis.
Area of Science:
- Molecular Biology
- Structural Biology
- Biochemistry
Background:
- N6-threonylcarbamoyladenosine (t6A) is a crucial tRNA modification for translational fidelity.
- Bacterial t6A biosynthesis involves TsaC/TsaC2, and a TC-transfer complex (TsaB, TsaD, TsaE).
Purpose of the Study:
- To elucidate the structure and mechanism of the bacterial TC-transfer complex.
- To understand the role of ATP hydrolysis in the t6A biosynthesis cycle.
Main Methods:
- X-ray crystallography of the Thermotoga maritima TC-transfer complex (TmTsaB2D2E2) with Mg2+-ATP and carboxy-AMP.
- Site-directed mutagenesis of TsaE.
- Small-angle X-ray scattering (SAXS) analysis of the TmTsaB2D2-tRNA complex.
Main Results:
- Determined the 2.5-Å crystal structure of TmTsaB2D2E2 bound to Mg2+-ATP and carboxy-AMP.
- Identified conserved Switch I and Switch II motifs in TsaE critical for ATP hydrolysis-driven reactivation.
- SAXS confirmed tRNA binding within the TsaE cavity.
Conclusions:
- Proposed a mechanistic model for TC transfer based on structural and biochemical data.
- Highlighted the importance of TsaE in the ATP-dependent t6A cycle.
- Provided insights into a universally conserved tRNA modification system.
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