The Mycobacterial MsDps2 Protein Is a Nucleoid-Forming DNA Binding Protein Regulated by Sigma Factors sA and sB

• Published in: PloS one 2009-11, Vol.4 (1)
• Main Authors: Saraswathi, Ramachandran, Pait Chowdhury, Rakhi, Williams, Sunanda Margrett, Ghatak, Payel, Chatterji, Dipankar
• Format: Article
• Language: English
• Subjects: atomic force microscopy; DNA-binding protein; DNA-directed RNA polymerase; Mycobacterium smegmatis; Nucleoids; Osmotic stress; Promoters; Sigma factor; Starvation; stationary phase
• ISSN: 1932-6203
• DOI: 10.1371/journal.pone.0008017

The Dps (DNA-binding protein from starved cells) proteins from Mycobacterium smegmatis MsDps1 and MsDps2 are both DNA-binding proteins with some differences. While MsDps1 has two oligomeric states, with one of them responsible for DNA binding, MsDps2 has only one DNA-binding oligomeric state. Both the proteins however, show iron-binding activity. The MsDps1 protein has been shown previously to be induced under conditions of starvation and osmotic stress and is regulated by the extra cellular sigma factors sH and sF. We show here, that the second Dps homologue in M. smegmatis, namely MsDps2, is purified in a DNA-bound form and exhibits nucleoid-like structures under the atomic force microscope. It appears that the N-terminal sequence of Dps2 plays a role in nucleoid formation. MsDps2, unlike MsDps1, does not show elevated expression in nutritionally starved or stationary phase conditions; rather its promoter is recognized by RNA polymerase containing sA or sB, under in vitro conditions. We propose that due to the nucleoid-condensing ability, the expression of MsDps2 is tightly regulated inside the cells.