Mutational analysis of L30. A. A schematic illustrating the primary sequences and predicted secondary structures of L30 and SBP2. The position numbers refer to the rat protein sequences. The L7Ae conserved RNA-binding domain is underlined and the conserved signature amino acid motifs for L30 and SBP2 are boxed as described in . Arrows indicate the amino acids in L30 that were mutated to alanine. B. The wild-type and mutant L30 protein were expressed in bacteria, purified and analyzed by SDS-PAGE and Coomassie Blue staining. The molecular weight markers are shown in the left lane of each gel.