The Positively Charged Active Site of the Bacterial Toxin RelE Causes a Large Shift in the General Base pK_a.

ABSTRACT: The bacterial toxin RelE cleaves mRNA in the ribosomal A site. Although it shares a global fold with other microbial RNases, the active site contains several positively charged residues instead of histidines and glutamates that are typical of ribonucleases. The pH dependences of wild-type and mutant RelE indicate it uses general acid-base catalysis, but either the general acid (proposed to be R81) or the general base must have a substantially downshifted pK_a. However, which group is shifted cannot be determined using available structural and biochemical data. Here, we use a phosphorothiolate at the scissile phosphate to remove the need for a general acid. We show this modification rescues nearly all of the defect of the R81A mutation, supporting R81 as the general acid. W

SUBMITTER: Hiller DA 

PROVIDER: S-EPMC7260706 | biostudies-literature | 2020 May

REPOSITORIES: biostudies-literature