Crystal Structure of RNase T, an Exoribonuclease Involved in tRNA Maturation and End Turnover

• DOI: 10.1016/j.str.2007.02.004
• Publication Date: 2007-04-18T11:33:10Z
• Authors: Yuhong Zuo; Heping Zheng; Yong Wang; Maksymilian Chruszcz; Marcin Cymborowski; Tatiana Skarina; Alexei Savchenko; Arun Malhotra; Wladek Minor
• Keywords: 0303 health sciences; 03 medical and health sciences; RNA, Transfer; Structural Biology; Exoribonucleases; Molecular Sequence Data; Pseudomonas aeruginosa; Escherichia coli; RNA; Amino Acid Sequence; Molecular Biology; 3. Good health

The 3' processing of most bacterial precursor tRNAs involves exonucleolytic trimming to yield a mature CCA end. This step is carried out by RNase T, a member of the large DEDD family of exonucleases. We report the crystal structures of RNase T from Escherichia coli and Pseudomonas aeruginosa, which show that this enzyme adopts an opposing dimeric arrangement, with the catalytic DEDD residues from one monomer closely juxtaposed with a large basic patch on the other monomer. This arrangement suggests that RNase T has to be dimeric for substrate specificity, and agrees very well with prior site-directed mutagenesis studies. The dimeric architecture of RNase T is very similar to the arrangement seen in oligoribonuclease, another bacterial DEDD family exoribonuclease. The catalytic residues in these two enzymes are organized very similarly to the catalytic domain of the third DEDD family exoribonuclease in E. coli, RNase D, which is monomeric.