Proteomics analysis of carbon-starved Mycobacterium smegmatis: induction of Dps-like protein

Abstract

Mycobacterium tuberculosis is a globally successful pathogen, infecting more than one third of total world's population. These bacteria have the remarkable ability to persist in the host for long periods of time unrecognized by the immune system and then to re-emerge later in life causing the disease. The physiology of such persistent or dormant bacilli is not very well characterized. Some evidence suggests that the dormant bacilli survive in a nutrient-deprived state that is similar to the stationary phase of the bacteria with respect to gene expression and physiology. Under this assumption we have studied the survival of Mycobacterium smegmatis in carbon starvation conditions as a model for mycobacterial persistence. M.smegmatis, being a fast-growing strain, serves as a good model to study starvation responses. Using the two-dimensional electrophoresis-based proteomics approach, we identified a protein which was found to be expressed preferentially under starvation conditions. This protein is homologous to a family of proteins called Dps (DNA binding Protein from Starved cells) that are known to protect DNA under various kinds of environmental stresses and its existence has, so far, not been reported in mycobacteria. Upon expression and purification of this protein, we observed that it has non-specific DNA-binding ability. Formation of a cage-like dodecamer structure is a characteristic feature of Dps. Using comparative modelling we were able to show that Dps from M.smegmatis could form a dodecamer structure similar to the crystal structure of Dps from Escherichia coli.

Reassessment of Protein Stability, DNA Binding, and Protection of Mycobacterium smegmatis Dps

“…Construction of DpsMs-His-An M. smegmatis Dps protein containing 6 histidines and an additional KPAAALE sequence at the C terminus was obtained by PCR using the primers described previously (20).…”

Mycobacterium tuberculosis: Dormancy, Persistence and Survival in the Light of Protein Synthesis

“…Although Dps kind of proteins have, so far, not been yet reported in mycobacteria, it is highly possible that similar system exists. Using comparative modelling it was possible to demonstrate that Dps from Mycobacterium smegmatis could form a dodecamer structure similar to the Dps from Escherichia coli (Gupta et al, 2002). The intriguing properties related to protein stability, DNA binding property and protection was further revisited to consolidate the structure function attribute of this unique protein (Ceci et al, 2005).…”

The multifunctional histone-like protein Lsr2 protects mycobacteria against reactive oxygen intermediates

“…Dps appears to protect DNA through the dual mechanisms of iron sequestration, which prevents Fentonmediated ROI generation and DNA binding, which compacts DNA and creates a protective physical barrier (8,9). Dps has been identified in a diverse group of bacteria, including Mycobacterium smegmatis (10); however, structural homologs have not been detected in the M. tuberculosis genome. This is relatively surprising given the importance of ROI in antituberculosis immunity.…”