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Single nucleotide polymorphism in the genes of mce1 and mce4 operons of Mycobacterium tuberculosis: analysis of clinical isolates and standard reference strains.

Pasricha R, Chandolia A, Ponnan P, Saini NK, Sharma S, Chopra M, Basil MV, Brahmachari V, Bose M - BMC Microbiol. (2011)

Bottom Line: The mutated Mce1A protein showed structural changes that could account for the effects of this mutation.Our results show that SNPs in the coding sequences of mce1 and mce4 operons in clinical isolates can be significantly high.Moreover, mce4 operon is significantly more polymorphic than mce1 operon (p < 0.001).

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Microbiology, Vallabhbhai Patel Chest Institute, University of Delhi, Delhi-110007, India.

ABSTRACT

Background: The presence of four mammalian cell entry (mce) operons in Mycobacterium tuberculosis suggests the essentiality of the functions of the genes in these operons. The differential expression of the four mce operons in different phases of in vitro growth and in infected animals reported earlier from our laboratory further justifies the apparent redundancy for these genes in the genome.Here we investigate the extent of polymorphism in eight genes in the mce1 and mce4 operons of M. tuberculosis from four standard reference strains (H37Rv, H37Ra, LVS (Low Virulent Strain) and BCG) and 112 clinical isolates varying in their drug susceptibility profile, analysed by direct sequencing and Sequenom MassARRAY platform.

Results: We discovered 20 single nucleotide polymorphisms (SNPs) in the two operons. The comparative analysis of the genes of mce1 and mce4 operons revealed that yrbE1A [Rv0167] was most polymorphic in mce1 operon while yrbE4A [Rv3501c] and lprN [Rv3495c] had the highest number of SNPs in the mce4 operon. Of 20 SNPs, 12 were found to be nonsynonymous and were further analysed for their pathological relevance to M. tuberculosis using web servers PolyPhen and PMut, which predicted five deleterious nonsynonymous SNPs. A mutation from proline to serine at position 359 of the native Mce1A protein was most deleterious as predicted by both PolyPhen and PMut servers. Energy minimization of the structure of native Mce1A protein and mutated protein was performed using InsightII. The mutated Mce1A protein showed structural changes that could account for the effects of this mutation.

Conclusions: Our results show that SNPs in the coding sequences of mce1 and mce4 operons in clinical isolates can be significantly high. Moreover, mce4 operon is significantly more polymorphic than mce1 operon (p < 0.001). However, the frequency of nonsynonymous substitutions is higher in mce1 operon and synonymous substitutions are more in mce4 operon. In silico modeling predict that nonsynonymous SNP at mce1A [Rv0169], a virulence gene could play a pivotal role in causing functional changes in M. tuberculosis that may reflect upon the biology of the bacteria.

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Related in: MedlinePlus

Wild and mutant protein structure of Mce1A. Structure of (A) wild (orange ribbon) and (B) Pro359Ser mutant (blue ribbon) proteins showing Pro359 (green) in wild protein and Ser359 (pink) in the mutant protein represented in ball and stick. The figure was prepared using Discovery studio 2.5 (DS Modeling 2.5, Accelrys Inc.: San Diego, CA).
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Figure 2: Wild and mutant protein structure of Mce1A. Structure of (A) wild (orange ribbon) and (B) Pro359Ser mutant (blue ribbon) proteins showing Pro359 (green) in wild protein and Ser359 (pink) in the mutant protein represented in ball and stick. The figure was prepared using Discovery studio 2.5 (DS Modeling 2.5, Accelrys Inc.: San Diego, CA).

Mentions: We selected C1075T (Pro359Ser) polymorphism in mce1A gene as shown in Table 1 for further structural analysis. The substitution is positioned at 359 amino acid and we have mapped this in the three dimensional structure [PDB: 1NA9] [16]. Mutation at the specified position was performed by InsightII/Biopolymer and energy minimizations were performed by InsightII/Discover module for both the native structure [PDB: 1NA9] and mutant modeled structure (Pro359Ser). This structural analysis shows that the native (Figure 2A) and the mutant (Figure 2B) protein structure has an RMSD of 3.07 Ǻ. It is interesting to observe that, in the native structure, Proline359 is a part of the helical conformation while the mutated counterpart (Pro359Ser) has a loop structure at this position (Figure 3). Perturbation in the hydrogen bonds as indicated in the HB plots (Figure 4A and 4B) could be attributed to the conformational changes at Ser 359 position and other regions of mutant protein.


Single nucleotide polymorphism in the genes of mce1 and mce4 operons of Mycobacterium tuberculosis: analysis of clinical isolates and standard reference strains.

Pasricha R, Chandolia A, Ponnan P, Saini NK, Sharma S, Chopra M, Basil MV, Brahmachari V, Bose M - BMC Microbiol. (2011)

Wild and mutant protein structure of Mce1A. Structure of (A) wild (orange ribbon) and (B) Pro359Ser mutant (blue ribbon) proteins showing Pro359 (green) in wild protein and Ser359 (pink) in the mutant protein represented in ball and stick. The figure was prepared using Discovery studio 2.5 (DS Modeling 2.5, Accelrys Inc.: San Diego, CA).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3050694&req=5

Figure 2: Wild and mutant protein structure of Mce1A. Structure of (A) wild (orange ribbon) and (B) Pro359Ser mutant (blue ribbon) proteins showing Pro359 (green) in wild protein and Ser359 (pink) in the mutant protein represented in ball and stick. The figure was prepared using Discovery studio 2.5 (DS Modeling 2.5, Accelrys Inc.: San Diego, CA).
Mentions: We selected C1075T (Pro359Ser) polymorphism in mce1A gene as shown in Table 1 for further structural analysis. The substitution is positioned at 359 amino acid and we have mapped this in the three dimensional structure [PDB: 1NA9] [16]. Mutation at the specified position was performed by InsightII/Biopolymer and energy minimizations were performed by InsightII/Discover module for both the native structure [PDB: 1NA9] and mutant modeled structure (Pro359Ser). This structural analysis shows that the native (Figure 2A) and the mutant (Figure 2B) protein structure has an RMSD of 3.07 Ǻ. It is interesting to observe that, in the native structure, Proline359 is a part of the helical conformation while the mutated counterpart (Pro359Ser) has a loop structure at this position (Figure 3). Perturbation in the hydrogen bonds as indicated in the HB plots (Figure 4A and 4B) could be attributed to the conformational changes at Ser 359 position and other regions of mutant protein.

Bottom Line: The mutated Mce1A protein showed structural changes that could account for the effects of this mutation.Our results show that SNPs in the coding sequences of mce1 and mce4 operons in clinical isolates can be significantly high.Moreover, mce4 operon is significantly more polymorphic than mce1 operon (p < 0.001).

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Microbiology, Vallabhbhai Patel Chest Institute, University of Delhi, Delhi-110007, India.

ABSTRACT

Background: The presence of four mammalian cell entry (mce) operons in Mycobacterium tuberculosis suggests the essentiality of the functions of the genes in these operons. The differential expression of the four mce operons in different phases of in vitro growth and in infected animals reported earlier from our laboratory further justifies the apparent redundancy for these genes in the genome.Here we investigate the extent of polymorphism in eight genes in the mce1 and mce4 operons of M. tuberculosis from four standard reference strains (H37Rv, H37Ra, LVS (Low Virulent Strain) and BCG) and 112 clinical isolates varying in their drug susceptibility profile, analysed by direct sequencing and Sequenom MassARRAY platform.

Results: We discovered 20 single nucleotide polymorphisms (SNPs) in the two operons. The comparative analysis of the genes of mce1 and mce4 operons revealed that yrbE1A [Rv0167] was most polymorphic in mce1 operon while yrbE4A [Rv3501c] and lprN [Rv3495c] had the highest number of SNPs in the mce4 operon. Of 20 SNPs, 12 were found to be nonsynonymous and were further analysed for their pathological relevance to M. tuberculosis using web servers PolyPhen and PMut, which predicted five deleterious nonsynonymous SNPs. A mutation from proline to serine at position 359 of the native Mce1A protein was most deleterious as predicted by both PolyPhen and PMut servers. Energy minimization of the structure of native Mce1A protein and mutated protein was performed using InsightII. The mutated Mce1A protein showed structural changes that could account for the effects of this mutation.

Conclusions: Our results show that SNPs in the coding sequences of mce1 and mce4 operons in clinical isolates can be significantly high. Moreover, mce4 operon is significantly more polymorphic than mce1 operon (p < 0.001). However, the frequency of nonsynonymous substitutions is higher in mce1 operon and synonymous substitutions are more in mce4 operon. In silico modeling predict that nonsynonymous SNP at mce1A [Rv0169], a virulence gene could play a pivotal role in causing functional changes in M. tuberculosis that may reflect upon the biology of the bacteria.

Show MeSH
Related in: MedlinePlus