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Abstract
RqkA, a DNA damage responsive serine/threonine kinase, is characterized for its role in DNA repair and cell division in D. radiodurans. It has a unique combination of a kinase domain at N-terminus and a WD40 type domain at C-terminus joined through a linker. WD40 domain is comprised of eight β-propeller repeats held together via ‘tryptophan-docking motifs’ and forming a typical ‘velcro’ closure structure. RqkA mutants lacking the WD40 region (hereafter referred to as WD mutant) could not complement RqkA loss in γ radiation resistance in D. radiodurans and lacked γ radiation-mediated activation of kinase activity in vivo. WD mutants failed to phosphorylate its cognate substrate (e.g. DrRecA) in surrogate E. coli cells. Unlike wild-type enzyme, the kinase activity of its WD40 mutants was not stimulated by pyrroloquinoline quinine (PQQ) indicating the role of the WD motifs in PQQ interaction and stimulation of its kinase activity. Together, results highlighted the importance of the WD40 domain in the regulation of RqkA kinase signaling functions in vivo, and thus, the role of WD40 domain in the regulation of any STPK is first time demonstrated in bacteria.
Communicated by Ramaswamy H. Sarma
Acknowledgement
Acknowledge the Department of Atomic Energy (DAE), Government of India for financial and structural support.
Authors contribution
D.K.S. did experiments, results analysis and discussion. S.C.B. did all computational and modeling work. M.Q.S. did docking studies. H.S.M. contributed in results analysis and discussion, and paper writing. Y.S.R. conceived the study, planning and execution of experiments, results analysis, discussion, paper writing, communication and correspondence for publication.
Disclosure statement
Authors have no conflict of interest on the content of manuscript.