Limits...
Studies of Toxoplasma gondii and Plasmodium falciparum enoyl acyl carrier protein reductase and implications for the development of antiparasitic agents.

Muench SP, Prigge ST, McLeod R, Rafferty JB, Kirisits MJ, Roberts CW, Mui EJ, Rice DW - Acta Crystallogr. D Biol. Crystallogr. (2007)

Bottom Line: The structures of T. gondii ENR have revealed that, as in its bacterial and plant homologues, a loop region which flanks the active site becomes ordered upon inhibitor binding, resulting in the slow tight binding of triclosan.Structural comparison of the apicomplexan ENR structures with their bacterial and plant counterparts has revealed that although the active sites of the parasite enzymes are broadly similar to those of their bacterial counterparts, there are a number of important differences within the drug-binding pocket that reduce the packing interactions formed with several inhibitors in the apicomplexan ENR enzymes.Together with other significant structural differences, this provides a possible explanation of the lower affinity of the parasite ENR enzyme family for aminopyridine-based inhibitors, suggesting that an effective antiparasitic agent may well be distinct from equivalent antimicrobials.

View Article: PubMed Central - HTML - PubMed

Affiliation: The Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, England.

ABSTRACT
Recent studies have demonstrated that submicromolar concentrations of the biocide triclosan arrest the growth of the apicomplexan parasites Plasmodium falciparum and Toxoplasma gondii and inhibit the activity of the apicomplexan enoyl acyl carrier protein reductase (ENR). The crystal structures of T. gondii and P. falciparum ENR in complex with NAD(+) and triclosan and of T. gondii ENR in an apo form have been solved to 2.6, 2.2 and 2.8 A, respectively. The structures of T. gondii ENR have revealed that, as in its bacterial and plant homologues, a loop region which flanks the active site becomes ordered upon inhibitor binding, resulting in the slow tight binding of triclosan. In addition, the T. gondii ENR-triclosan complex reveals the folding of a hydrophilic insert common to the apicomplexan family that flanks the substrate-binding domain and is disordered in all other reported apicomplexan ENR structures. Structural comparison of the apicomplexan ENR structures with their bacterial and plant counterparts has revealed that although the active sites of the parasite enzymes are broadly similar to those of their bacterial counterparts, there are a number of important differences within the drug-binding pocket that reduce the packing interactions formed with several inhibitors in the apicomplexan ENR enzymes. Together with other significant structural differences, this provides a possible explanation of the lower affinity of the parasite ENR enzyme family for aminopyridine-based inhibitors, suggesting that an effective antiparasitic agent may well be distinct from equivalent antimicrobials.

Show MeSH

Related in: MedlinePlus

A structure-based sequence alignment of the ENR enzymes from P. falciparum, P. knowlesi, P. vivax, P. chabaudi, P. yoelii, B. napus, E. coli, M. tuberculosis and T. gondii. The elements of secondary structure and the sequence numbering, which is from the start of the mature enzyme for the P. falciparum and T. gondii enzymes, are shown above and below the alignment, respectively, with cylinders representing α-helices and arrows β-strands. Residues fully conserved in the above sequences are shown in black boxes and residues which are within 4 Å of the inhibitor triclosan are highlighted by a black circle. Those residues which form the conserved SGE motif (residues 238–240 in TgENR) are enclosed by a black box.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2483495&req=5

fig2: A structure-based sequence alignment of the ENR enzymes from P. falciparum, P. knowlesi, P. vivax, P. chabaudi, P. yoelii, B. napus, E. coli, M. tuberculosis and T. gondii. The elements of secondary structure and the sequence numbering, which is from the start of the mature enzyme for the P. falciparum and T. gondii enzymes, are shown above and below the alignment, respectively, with cylinders representing α-helices and arrows β-strands. Residues fully conserved in the above sequences are shown in black boxes and residues which are within 4 Å of the inhibitor triclosan are highlighted by a black circle. Those residues which form the conserved SGE motif (residues 238–240 in TgENR) are enclosed by a black box.

Mentions: Sequence alignment of T. gondii and Plasmodium ENRs reveals considerable similarity to the enzymes from other species, with the closest resemblance being to those of plant rather than bacterial origin, with for example approximately 50% sequence identity between Brassica napus and T. gondii ENR (Fig. 2 ▶). Compared with other ENRs, a striking feature of the Plasmodium ENR enzymes is the presence of a large polar low-complexity insert of variable size which is thought to flank the substrate-binding pocket. In T. gondii ENR, a similar but smaller insert consisting of only six residues can be observed. In the bacterial enzymes, only the ENR from Mycobacterium tuberculosis (MtENR) shows a significant insert at this position. However, in MtENR this insert has been implicated in allowing the enzyme to accommodate larger substrates such as mycolic fatty acids (Rozwarski et al., 1999 ▶) and its glycine-rich hydrophobic nature is in contrast to that found in the apicomplexan ENRs, which contain a predominantly polar hydrophilic insert of unknown function.


Studies of Toxoplasma gondii and Plasmodium falciparum enoyl acyl carrier protein reductase and implications for the development of antiparasitic agents.

Muench SP, Prigge ST, McLeod R, Rafferty JB, Kirisits MJ, Roberts CW, Mui EJ, Rice DW - Acta Crystallogr. D Biol. Crystallogr. (2007)

A structure-based sequence alignment of the ENR enzymes from P. falciparum, P. knowlesi, P. vivax, P. chabaudi, P. yoelii, B. napus, E. coli, M. tuberculosis and T. gondii. The elements of secondary structure and the sequence numbering, which is from the start of the mature enzyme for the P. falciparum and T. gondii enzymes, are shown above and below the alignment, respectively, with cylinders representing α-helices and arrows β-strands. Residues fully conserved in the above sequences are shown in black boxes and residues which are within 4 Å of the inhibitor triclosan are highlighted by a black circle. Those residues which form the conserved SGE motif (residues 238–240 in TgENR) are enclosed by a black box.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2483495&req=5

fig2: A structure-based sequence alignment of the ENR enzymes from P. falciparum, P. knowlesi, P. vivax, P. chabaudi, P. yoelii, B. napus, E. coli, M. tuberculosis and T. gondii. The elements of secondary structure and the sequence numbering, which is from the start of the mature enzyme for the P. falciparum and T. gondii enzymes, are shown above and below the alignment, respectively, with cylinders representing α-helices and arrows β-strands. Residues fully conserved in the above sequences are shown in black boxes and residues which are within 4 Å of the inhibitor triclosan are highlighted by a black circle. Those residues which form the conserved SGE motif (residues 238–240 in TgENR) are enclosed by a black box.
Mentions: Sequence alignment of T. gondii and Plasmodium ENRs reveals considerable similarity to the enzymes from other species, with the closest resemblance being to those of plant rather than bacterial origin, with for example approximately 50% sequence identity between Brassica napus and T. gondii ENR (Fig. 2 ▶). Compared with other ENRs, a striking feature of the Plasmodium ENR enzymes is the presence of a large polar low-complexity insert of variable size which is thought to flank the substrate-binding pocket. In T. gondii ENR, a similar but smaller insert consisting of only six residues can be observed. In the bacterial enzymes, only the ENR from Mycobacterium tuberculosis (MtENR) shows a significant insert at this position. However, in MtENR this insert has been implicated in allowing the enzyme to accommodate larger substrates such as mycolic fatty acids (Rozwarski et al., 1999 ▶) and its glycine-rich hydrophobic nature is in contrast to that found in the apicomplexan ENRs, which contain a predominantly polar hydrophilic insert of unknown function.

Bottom Line: The structures of T. gondii ENR have revealed that, as in its bacterial and plant homologues, a loop region which flanks the active site becomes ordered upon inhibitor binding, resulting in the slow tight binding of triclosan.Structural comparison of the apicomplexan ENR structures with their bacterial and plant counterparts has revealed that although the active sites of the parasite enzymes are broadly similar to those of their bacterial counterparts, there are a number of important differences within the drug-binding pocket that reduce the packing interactions formed with several inhibitors in the apicomplexan ENR enzymes.Together with other significant structural differences, this provides a possible explanation of the lower affinity of the parasite ENR enzyme family for aminopyridine-based inhibitors, suggesting that an effective antiparasitic agent may well be distinct from equivalent antimicrobials.

View Article: PubMed Central - HTML - PubMed

Affiliation: The Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, England.

ABSTRACT
Recent studies have demonstrated that submicromolar concentrations of the biocide triclosan arrest the growth of the apicomplexan parasites Plasmodium falciparum and Toxoplasma gondii and inhibit the activity of the apicomplexan enoyl acyl carrier protein reductase (ENR). The crystal structures of T. gondii and P. falciparum ENR in complex with NAD(+) and triclosan and of T. gondii ENR in an apo form have been solved to 2.6, 2.2 and 2.8 A, respectively. The structures of T. gondii ENR have revealed that, as in its bacterial and plant homologues, a loop region which flanks the active site becomes ordered upon inhibitor binding, resulting in the slow tight binding of triclosan. In addition, the T. gondii ENR-triclosan complex reveals the folding of a hydrophilic insert common to the apicomplexan family that flanks the substrate-binding domain and is disordered in all other reported apicomplexan ENR structures. Structural comparison of the apicomplexan ENR structures with their bacterial and plant counterparts has revealed that although the active sites of the parasite enzymes are broadly similar to those of their bacterial counterparts, there are a number of important differences within the drug-binding pocket that reduce the packing interactions formed with several inhibitors in the apicomplexan ENR enzymes. Together with other significant structural differences, this provides a possible explanation of the lower affinity of the parasite ENR enzyme family for aminopyridine-based inhibitors, suggesting that an effective antiparasitic agent may well be distinct from equivalent antimicrobials.

Show MeSH
Related in: MedlinePlus