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Mycobacterium smegmatis Ku binds zinc
Author(s) -
Kushwaha Ambuj Kumar,
Grove Anne
Publication year - 2013
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.27.1_supplement.1015.4
Subject(s) - zinc finger , mycobacterium smegmatis , zinc , dna , zinc finger nuclease , structural motif , biochemistry , binding site , chemistry , biology , biophysics , gene , transcription factor , mycobacterium tuberculosis , medicine , tuberculosis , organic chemistry , pathology
Ku protein is an important component of the non‐homologous end‐joining (NHEJ) pathway of DNA double strand break repair. Previously thought to be encoded only by eukaryotes, homologues of Ku protein have been identified in some bacterial species. The overall three dimensional topology of Ku is conserved from prokaryotes to eukaryotes and includes a central core consisting of a β‐barrel domain, pillar and bridge regions that together form a ring‐like structure. The bridge‐region is an extension of the β‐barrel core, which is well conserved and important for dimerization and DNA‐binding. Sequence analysis has revealed that the bridge‐region of Ku from several Gram‐positive bacteria and bacteriophages contains a potential zinc‐binding site with conventional HxxC and CxxC (where x is any residue) zinc binding motif, that belongs to a new family of zinc‐ribbon folding domain, suggested to be derived from a regular Zn‐ribbon by a segment‐swapping event. Interestingly, these sites have either deteriorated or been entirely lost in Ku from other organisms. Using an in vitro metal binding assay we have shown that M. smegmatis Ku binds zinc. Also, we observed that zinc binding stabilizes the Ku protein and protects it from oxidative damage. Based on our finding, we predict that retention of zinc binding site in Ku proteins from M. smegmatis and other related gram‐positive bacterial species might also provide protection against zinc toxicity.