Structure of a bacterial ribonuclease P holoenzyme in complex with tRNA

Area of Science:

• Biochemistry
• Structural Biology
• Molecular Biology

Background:

• Ribonuclease P (RNase P) is a vital enzyme responsible for tRNA 5'-end maturation.
• RNase P is a ribozyme, meaning its catalytic activity is primarily RNA-based.
• Understanding the structure of RNase P is key to deciphering its catalytic mechanism.

Purpose of the Study:

• To determine the high-resolution crystal structure of the Thermotoga maritima RNase P holoenzyme in complex with tRNA(Phe).
• To elucidate the molecular interactions governing substrate recognition and catalysis.
• To provide insights into the universal mechanism of RNase P function.

Main Methods:

• X-ray crystallography was employed to obtain the structure of the 154 kDa RNase P-tRNA complex.
• Soaking experiments with pre-tRNA and metal ions were performed to identify substrate binding and catalytic sites.
• Structural analysis focused on RNA-RNA interactions, protein-RNA interfaces, and active site composition.

Main Results:

• The crystal structure reveals intricate RNA-RNA recognition through shape complementarity, specific contacts, and base pairing.
• The protein cofactor binds to a conserved RNA module and interacts with the pre-tRNA leader sequence, not the mature tRNA.
• The active site comprises phosphate backbone elements, a conserved uridine, and essential metal ions, indicating a conserved catalytic mechanism.

Conclusions:

• The study provides a detailed structural basis for RNase P-mediated tRNA processing.
• The findings highlight the roles of both RNA and protein components in substrate binding and catalysis.
• The conserved features suggest a universal catalytic mechanism for RNase P across different organisms.