Title |
Functional and structural characterization of Deinococcus radiodurans R1 MazEF toxin-antitoxin system, Dr0416-Dr0417 |
Author |
Immanuel Dhanasingh1, Eunsil Choi2, Jeongeun Lee2, Sung Haeng Lee1*, and Jihwan Hwang2* |
Address |
1Department of Cellular and Molecular Medicine, Chosun University School of Medicine, Gwangju 61452, Republic of Korea, 2Department of Microbiology, Pusan National University, Busan 46241, Republic of Korea |
Bibliography |
Journal of Microbiology, 59(2),186–201, 2021,
|
DOI |
10.1007/s12275-021-0523-z
|
Key Words |
Deinococcus radiodurans, toxin, antitoxin, MazF,
RNA cleavage |
Abstract |
In prokaryotes, toxin-antitoxin (TA) systems are commonly
found. They likely reflect the adaptation of pathogenic bacteria
or extremophiles to various unfavorable environments
by slowing their growth rate. Genomic analysis of the extremophile
Deinococcus radiodurans R1 revealed the presence of
eight type II TA systems, including the genes dr0417, dr0660,
dr1530, dr0690, and dr1807. Expression of these toxin genes
led to inhibition of Escherichia coli growth, whereas their
antidote antitoxins were able to recover the growth defect.
Remarkably, Dr0417 (DrMazF) showed endoribonuclease activity
toward rRNAs as well as mRNAs, as determined by in
vivo and in vitro RNA cleavage assays, and this activity was
inhibited by Dr0416 (DrMazE). It was also found that the expression
of dr0416-0417 module is directly regulated by the
DrMazE-MazF complex. Furthermore, this TA module was
induced under stress conditions and plays an important role
in survival. To understand the regulatory mechanism at the
molecular level, we determined the first high-resolution structures
of DrMazF alone and of the DrMazE-MazF complex.
In contrast with the hetero-hexameric state of typical MazEMazF
complexes found in other species, DrMazE-MazF crystal
structure consists of a hetero-trimer, with the DNA-binding
domain of DrMazE undergoing self-cleavage at the flexible
linker loop. Our structure revealed that the unique residue
R54 provides an additional positive charge to the substratebinding
pocket of DrMazF, its mutation significantly affects
the endonuclease activity. Thus, our work reports the unique
structural and biochemical features of the DrMazE-MazF
system. |