Structure of the RNA-processing inhibitor RraA from Thermus thermophilis.

The menG gene product, thought to catalyze the final methylation in vitamin K(2) synthesis, has recently been shown to inhibit RNase E in Eschericha coli. The structure of the protein, since renamed RraA, has been solved to 2.3 A using the multiple-wavelength anomalous diffraction method and selenomethionine-substituted protein from Thermus thermophilus. The six molecules in the asymmetric unit are arranged as two similar trimers which have a degree of interaction, suggesting biological significance. The fold does not support the postulated methylation function. Genomic analysis, specifically a lack of an RNase E homologue in cases where homologues to RraA exist, indicates that the function is still obscure.