Protein components contribute to active site architecture for eukaryotic ribonuclease P

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• Eukaryotic ribonuclease P (RNase P) is essential for tRNA maturation.
• Unlike bacterial RNase P, eukaryotic RNase P requires both RNA and protein components for activity.
• Eukaryotic RNase P RNA alone lacks intrinsic catalytic activity.

Purpose of the Study:

• To investigate the substrate-binding environment of eukaryotic RNase P holoenzymes.
• To compare substrate interactions between eukaryotic and bacterial RNase P.
• To identify differences in holoenzyme organization.

Main Methods:

• Photoreactive cross-linking assay using [4-thio]-uridine-labeled pre-tRNAGln.
• Analysis of cross-linking products with Tetrahymena thermophila, human, and E. coli RNase P holoenzymes.
• Testing cross-linking with isolated HeLa RNase P RNA.

Main Results:

• Protein components of Tetrahymena thermophila and human RNase P formed specific cross-links with pre-tRNAGln.
• HeLa RNase P RNA did not form cross-links, even with associated proteins.
• Escherichia coli RNase P RNA specifically formed photoadducts with the substrate.

Conclusions:

• Eukaryotic RNase P holoenzymes feature a protein-rich active site for substrate binding.
• Bacterial RNase P RNA binds substrates independently, differing from eukaryotic holoenzymes.
• This protein-dependent substrate interaction is a distinguishing feature of eukaryotic RNase P.