Substrate recognition and cleavage-site selection by a single-subunit protein-only RNase P

Area of Science:

• Molecular Biology
• Enzymology
• Evolutionary Biology

Background:

• Ribonuclease P (RNase P) enzymes process transfer RNA (tRNA) precursors by removing 5' extensions.
• RNase P enzymes exhibit diverse forms, including protein-only and RNA-based ribonucleoproteins, making them a model for studying enzymatic evolution.
• The plant nuclear enzyme PRORP3 is a single-subunit proteinaceous RNase P.

Purpose of the Study:

• To investigate substrate recognition and cleavage-site selection by Arabidopsis thaliana RNase P PRORP3.
• To compare the catalytic mechanism of the protein-only PRORP3 with other RNase P forms, particularly bacterial RNase P.

Main Methods:

• Biochemical analysis of substrate binding and cleavage site determination for PRORP3.
• Comparative analysis of PRORP3's mechanism against known bacterial RNase P mechanisms.

Main Results:

• PRORP3 requires a larger portion of the intact tRNA structure for recognition compared to bacterial RNase P.
• PRORP3 shows minimal dependence on specific cleavage site determinants or interactions with tRNA 5'/3' extensions.
• Cleavage site selection by PRORP3 is influenced by the acceptor stem and T domain dimensions and requires a single-stranded leader sequence.

Conclusions:

• The single-subunit PRORP3 enzyme mechanism shares more similarities with complex nuclear RNase P ribonucleoproteins than with simpler bacterial RNase P.
• Mechanistic similarities or differences among RNase P forms do not necessarily correlate with their molecular composition or evolutionary relationships.