Distinct properties of Mycobacterium tuberculosis single-stranded DNA binding protein and its functional characterization in Escherichia coli

Single-stranded DNA binding proteins (SSBs) play an essential role in vario us DNA functions, Characterization of SSB from Mycobacterium tuberculosis, which infects nearly one-third of the world's population and kills about 2- 3 million people every year, showed that its oligomeric state and various i n vitro DNA binding properties were similar to those of the SSB from Escher ichia coil, In this study, use of the yeast two-hybrid assay suggests that the EcoSSB and the MtuSSB are even capable of heterooligomerization. Howeve r, the MtuSSB failed to complement a Delta ssb strain of E. coli, The seque nce comparison suggested that MtuSSB contained a distinct C-terminal domain , The C-terminal domain of EcoSSB interacts with various cellular proteins. The chimeric constructs between the N- and C-terminal domains of the MtuSS B and EcoSSB exist as homotetramers and demonstrate DNA binding properties similar to the wild-type counterparts. Despite similar biochemical properti es, the chimeric SSBs also failed to complement the Delta ssb strain of E,c oli, These data allude to the occurrence of a 'cross talk' between the N- a nd the C-terminal domains of the SSBs for their in vivo function, Further, compared with those of the EcoSSB, the secondary/tertiary interactions with in MtuSSB were found to be less susceptible to disruption by guanidinium hy drochloride, Such structural differences could be exploited for utilizing s uch essential proteins as crucial molecular targets for controlling the gro wth of the pathogen.