A novel nucleoid-associated protein of Mycobacterium tuberculosis is a sequence homolog of GroEL

Debashree Basu, Garima Khare, Shashi Singh, Anil Tyagi, Sanjeev Khosla, Shekhar C. Mande

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The Mycobacterium tuberculosis genome sequence reveals remarkable absence of many nucleoid-associated proteins (NAPs), such as HNS, Hfq or DPS. In order to characterize the nucleoids of M. tuberculosis, we have attempted to identify NAPs, and report an interesting finding that a chaperonin-homolog, GroEL1, is nucleoid associated. We report that M. tuberculosis GroEL1 binds DNA with low specificity but high affinity, suggesting that it might have naturally evolved to bind DNA. We are able to demonstrate that GroEL1 can effectively function as a DNA-protecting agent against DNase I or hydroxyl-radicals. Moreover, Atomic Force Microscopic studies reveal that GroEL1 can condense a large DNA into a compact structure. We also provide in vivo evidences that include presence of GroEL1 in purified nucleoids, in vivo crosslinking followed by Southern hybridizations and immunofluorescence imaging in M. tuberculosis confirming that GroEL1: DNA interactions occur in natural biological settings. These findings therefore reveal that M. tuberculosis GroEL1 has evolved to be associated with nucleoids.

Original languageEnglish (US)
Pages (from-to)4944-4954
Number of pages11
JournalNucleic acids research
Issue number15
StatePublished - 2009

Bibliographical note

Funding Information:
Department of Biotechnology, India; Wellcome Trust, UK; Council for Scientific and Industrial Research Senior Research Fellowships (to D.B. and G.K.); Wellcome Trust International Senior Research Fellowship (to S.C.M.). Funding for open access charge: Wellcome Trust grant WT070006MA.


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