Abstract
The characteristic fold of a protein is the decisive factor for its biological function. However, small structural changes to amino acids can also affect their function, for example in the case of post-translational modification (PTM). Many different types of PTMs are known, but for some, including chlorination, studies elucidating their importance are limited. A recent study revealed that the YjgF/YER057c/UK114 family (YjgF family) member RidA from Escherichia coli shows chaperone activity after chlorination. Thus, to identify the functional and structural differences of RidA upon chlorination, we studied an RidA homolog from Staphylococcus aureus: YabJ. The overall structure of S. aureus YabJ was similar to other members of the YjgF family, showing deep pockets on its surface, and the residues composing the pockets were well conserved. S. aureus YabJ was highly stable after chlorination, and the chlorinated state is reversible by treatment with DTT. However, it shows no chaperone activity after chlorination. Instead, YabJ from S. aureus shows chlorination-induced ribonuclease activity, and the activity is diminished after subsequent reduction. Even though the yabJ genes from Staphylococcus and Bacillus are clustered with regulators that are expected to code nucleic acid-interacting proteins, the nucleic acid-related activity of bacterial RidA has not been identified before. From our study, we revealed the structure and function of S. aureus YabJ as a novel chlorination-activated ribonuclease. The present study will contribute to an in-depth understanding of chlorination as a PTM.
Highlights
Post-translational modification (PTM) is a biochemical process where amino acids of proteins are covalently modified after translation
A recent study revealed that Escherichia coli RidA from the YjgF/YER057c/UK114 family (YjgF family hereafter) exhibits chlorination-induced chaperone activity [5]
Each SAYabJ monomer consists of a β-sheet and two α-helices
Summary
Post-translational modification (PTM) is a biochemical process where amino acids of proteins are covalently modified after translation. We elucidated the crystal structure of SAYabJ from Staphylococcus aureus Mu50 and its function as a ribonuclease after chlorination. In the crystal structure of SAYabJ, all six footprint residues are positioned toward the deep pocket on the surface, where they are known to be involved in ligand binding (Figure 2).
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