Comparison of mammalian cell entry operons of mycobacteria: in silico analysis and expression profiling.
Mammalian cell entry (mce) operons, implicated in the entry of mycobacteria into host cells, are present in pathogenic and saprophytic species. It is likely that the genes in these operons have functions other than those required for entry into host cells. Using in silico analysis we have identified domains within the mce operons that might justify their occurrence in saprophytic species like Mycobacterium smegmatis. Our analysis identified in addition to the mce domain, the presence of the Ttg2B and Ttg2C domains, typical of proteins involved in transport. We have also analysed and compared the expression profile between mce operons of Mycobacterium tuberculosis, Mycobacterium bovis and M. smegmatis under different growth conditions. In case of M. smegmatis, each operon presented domain truncation for at least one gene. We observe differential expression among the operons in M. smegmatis growing under different culture conditions. Bacilli growing in nutritionally rich medium with aeration, only the mce4 operon was expressed while during stationary phase of a standing culture, all four mce operons were expressed. In M. bovis, in addition to the absence of the mce3 operon, several protein domains encoded by the other operons were truncated. We detected expression of the mce2 operon in the exponential and stationary growth phase, while the mce1 operon was only expressed in the stationary growth phase. Differential expression of mce operons and their redundancy in the genome of the majority members of mycobacteria are discussed in view of our results.
Kumar
Ashwani
A
Department of Microbiology, Vallabh Bhai Patel Chest Institute, Delhi University, Delhi 110007, India.
Chandolia
Amita
A
Chaudhry
Uma
U
Brahmachari
Vani
V
Bose
Mridula
M
D000942:Antigens, Bacterial / Q000096:biosynthesis / Q000235:genetics; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics*; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics; D019295:Computational Biology; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D009161:Mycobacterium / Q000235:genetics* / Q000378:metabolism; D009163:Mycobacterium bovis / Q000235:genetics / Q000378:metabolism; D020102:Mycobacterium smegmatis / Q000235:genetics / Q000378:metabolism; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000378:metabolism; D009876:Operon; D017434:Protein Structure, Tertiary / Q000235:genetics; D017384:Sequence Deletion
D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D002352:Carrier Proteins; C473802:mammalian cell entry protein Mce1A, Mycobacterium tuberculosis; C443482:mce2 protein, Mycobacterium tuberculosis