One of the hallmarks of life is the widespread use of certain
essential ribozymes. The ubiquitous ribonuclease P (RNase P) and
eukaryotic RNase MRP are essential complexes where a structured,
noncoding RNA acts in catalysis. Recent discoveries have
elucidated the three-dimensional structure of the ancestral
ribonucleoprotein complex, suggested the possibility of a
protein-only composition in organelles, and even noted the
absence of RNase P in a non-free-living organism. With respect
to these last two findings, import mechanisms for RNases P/MRP
into mitochondria have been demonstrated, and RNase P is present
in organisms with some of the smallest known genomes. Together,
these results have led to an ongoing debate regarding the
precise definition of how essential these ribozymes truly are.
(C) IUBMB IUBMB Life, 2012.