A novel nucleoid-associated protein of Mycobacterium tuberculosis is a sequence homolog of GroEL.
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.
Basu
Debashree
D
Laboratory of Structural Biology, Centre for DNA Fingerprinting and Diagnostics, Hyderabad 500001, India.
Khare
Garima
G
Singh
Shashi
S
Tyagi
Anil
A
Khosla
Sanjeev
S
Mande
Shekhar C
SC
D001426:Bacterial Proteins / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D018834:Chaperonin 60 / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D002876:Chromosomes, Bacterial / Q000737:chemistry; D004247:DNA / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D004277:DNA, Single-Stranded / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D009169:Mycobacterium tuberculosis / Q000235:genetics*; D009690:Nucleic Acid Conformation
D001426:Bacterial Proteins; D018834:Chaperonin 60; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D004247:DNA