Structural and biochemical characteristics of two Staphylococcus epidermidis RNase J paralogs RNase J1 and RNase J2.

RNase J enzymes are metallohydrolases that are involved in RNA maturation and RNA recycling, govern gene expression in bacteria, and catalyze both exonuclease and endonuclease activity. The catalytic activity of RNase J is regulated by multiple mechanisms which include oligomerization, conformational changes to aid substrate recognition, and the metal cofactor at the active site. However, little is known of how RNase J paralogs differ in expression and activity. Here we describe structural and biochemical features of two Staphylococcus epidermidis RNase J paralogs, RNase J1 and RNase J2. RNase J1 is a homodimer with exonuclease activity aided by two metal cofactors at the active site. RNase J2, on the other hand, has endonuclease activity and one metal ion at the active site and is predominantly a monomer. We note that the expression levels of these enzymes vary across Staphylococcal strains. Together, these observations suggest that multiple interacting RNase J paralogs could provide a strategy for functional improvisation utilizing differences in intracellular concentration, quaternary structure, and distinct active site architecture despite overall structural similarity.