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Crystal structures of Mycobacterium tuberculosis GlgE and complexes with non-covalent inhibitors.

Lindenberger JJ, Veleti SK, Wilson BN, Sucheck SJ, Ronning DR - Sci Rep (2015)

Bottom Line: The maltohexaose structure reveals a dominant site for α-glucan binding.To obtain more detailed interactions between first generation, non-covalent inhibitors and GlgE, a variant Streptomyces coelicolor GlgEI (Sco GlgEI-V279S) was made to better emulate the Mtb GlgE M1P binding site.These structures detail important interactions that contribute to the inhibitory activity of these compounds, and provide information on future designs that may be exploited to improve upon these first generation GlgE inhibitors.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry and Biochemistry, The University of Toledo, 2801 W. Bancroft St. Ms602, Toledo, OH, United States.

ABSTRACT
GlgE is a bacterial maltosyltransferase that catalyzes the elongation of a cytosolic, branched α-glucan. In Mycobacterium tuberculosis (M. tb), inactivation of GlgE (Mtb GlgE) results in the rapid death of the organism due to a toxic accumulation of the maltosyl donor, maltose-1-phosphate (M1P), suggesting that GlgE is an intriguing target for inhibitor design. In this study, the crystal structures of the Mtb GlgE in a binary complex with maltose and a ternary complex with maltose and a maltosyl-acceptor molecule, maltohexaose, were solved to 3.3 Å and 4.0 Å, respectively. The maltohexaose structure reveals a dominant site for α-glucan binding. To obtain more detailed interactions between first generation, non-covalent inhibitors and GlgE, a variant Streptomyces coelicolor GlgEI (Sco GlgEI-V279S) was made to better emulate the Mtb GlgE M1P binding site. The structure of Sco GlgEI-V279S complexed with α-maltose-C-phosphonate (MCP), a non-hydrolyzable substrate analogue, was solved to 1.9 Å resolution, and the structure of Sco GlgEI-V279S complexed with 2,5-dideoxy-3-O-α-D-glucopyranosyl-2,5-imino-D-mannitol (DDGIM), an oxocarbenium mimic, was solved to 2.5 Å resolution. These structures detail important interactions that contribute to the inhibitory activity of these compounds, and provide information on future designs that may be exploited to improve upon these first generation GlgE inhibitors.

No MeSH data available.


Related in: MedlinePlus

Mtb GlgE M1P donor site.(A) The M1P donor sites of the Mtb GlgE (green) and Sco GlgEI (cyan) with the active site nucleophile and maltose bound. (B) Both donor sites are highly conserved with the only difference being the presence of a serine (S303) in the Mtb GlgE, while a valine (V279) is present in the Sco GlgEI.
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f2: Mtb GlgE M1P donor site.(A) The M1P donor sites of the Mtb GlgE (green) and Sco GlgEI (cyan) with the active site nucleophile and maltose bound. (B) Both donor sites are highly conserved with the only difference being the presence of a serine (S303) in the Mtb GlgE, while a valine (V279) is present in the Sco GlgEI.

Mentions: The M1P binding sites of both enzymes are highly conserved in sequence and structure (Fig. 2A). This site is divided into two parts: the −1 subsite where the reducing end of maltose or the phospho-glucosyl moiety of the M1P substrate binds, and the −2 subsite where the non-reducing glucosyl moiety is bound9. Both the Mtb and Sco GlgE homologs exhibit a similar set of interactions that coordinate the maltose and position it within the M1P binding site due to the high level of amino acid conservation in the M1P binding site. The only residue that differs between the Mtb GlgE and Sco GlgEI M1P binding sites is represented by S303 and V279, respectively. In both orthologs, the corresponding residue is positioned within the −2 subsite. In the Mtb GlgE, S303 forms a hydrogen bonded interaction with the endocyclic O5 oxygen atom of the −2 glucose in the Mtb GlgE-MAL complex (Fig. 2B). In the Sco GlgEI, the corresponding V279 residue protrudes into the M1P binding site in the same orientation as the Mtb GlgE S303 residue (Fig. 2B). Rather than forming a hydrogen bond with substrate, V279 of Sco GlgEI forms a van der Waals interaction with two carbon atoms in the ring bound in the −2 subsite. This difference affects neither the active site structure nor the KMapp for M1P observed for Mtb GlgE, Sco GlgEI, or Sco GlgEI-V279S5710.


Crystal structures of Mycobacterium tuberculosis GlgE and complexes with non-covalent inhibitors.

Lindenberger JJ, Veleti SK, Wilson BN, Sucheck SJ, Ronning DR - Sci Rep (2015)

Mtb GlgE M1P donor site.(A) The M1P donor sites of the Mtb GlgE (green) and Sco GlgEI (cyan) with the active site nucleophile and maltose bound. (B) Both donor sites are highly conserved with the only difference being the presence of a serine (S303) in the Mtb GlgE, while a valine (V279) is present in the Sco GlgEI.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4526890&req=5

f2: Mtb GlgE M1P donor site.(A) The M1P donor sites of the Mtb GlgE (green) and Sco GlgEI (cyan) with the active site nucleophile and maltose bound. (B) Both donor sites are highly conserved with the only difference being the presence of a serine (S303) in the Mtb GlgE, while a valine (V279) is present in the Sco GlgEI.
Mentions: The M1P binding sites of both enzymes are highly conserved in sequence and structure (Fig. 2A). This site is divided into two parts: the −1 subsite where the reducing end of maltose or the phospho-glucosyl moiety of the M1P substrate binds, and the −2 subsite where the non-reducing glucosyl moiety is bound9. Both the Mtb and Sco GlgE homologs exhibit a similar set of interactions that coordinate the maltose and position it within the M1P binding site due to the high level of amino acid conservation in the M1P binding site. The only residue that differs between the Mtb GlgE and Sco GlgEI M1P binding sites is represented by S303 and V279, respectively. In both orthologs, the corresponding residue is positioned within the −2 subsite. In the Mtb GlgE, S303 forms a hydrogen bonded interaction with the endocyclic O5 oxygen atom of the −2 glucose in the Mtb GlgE-MAL complex (Fig. 2B). In the Sco GlgEI, the corresponding V279 residue protrudes into the M1P binding site in the same orientation as the Mtb GlgE S303 residue (Fig. 2B). Rather than forming a hydrogen bond with substrate, V279 of Sco GlgEI forms a van der Waals interaction with two carbon atoms in the ring bound in the −2 subsite. This difference affects neither the active site structure nor the KMapp for M1P observed for Mtb GlgE, Sco GlgEI, or Sco GlgEI-V279S5710.

Bottom Line: The maltohexaose structure reveals a dominant site for α-glucan binding.To obtain more detailed interactions between first generation, non-covalent inhibitors and GlgE, a variant Streptomyces coelicolor GlgEI (Sco GlgEI-V279S) was made to better emulate the Mtb GlgE M1P binding site.These structures detail important interactions that contribute to the inhibitory activity of these compounds, and provide information on future designs that may be exploited to improve upon these first generation GlgE inhibitors.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry and Biochemistry, The University of Toledo, 2801 W. Bancroft St. Ms602, Toledo, OH, United States.

ABSTRACT
GlgE is a bacterial maltosyltransferase that catalyzes the elongation of a cytosolic, branched α-glucan. In Mycobacterium tuberculosis (M. tb), inactivation of GlgE (Mtb GlgE) results in the rapid death of the organism due to a toxic accumulation of the maltosyl donor, maltose-1-phosphate (M1P), suggesting that GlgE is an intriguing target for inhibitor design. In this study, the crystal structures of the Mtb GlgE in a binary complex with maltose and a ternary complex with maltose and a maltosyl-acceptor molecule, maltohexaose, were solved to 3.3 Å and 4.0 Å, respectively. The maltohexaose structure reveals a dominant site for α-glucan binding. To obtain more detailed interactions between first generation, non-covalent inhibitors and GlgE, a variant Streptomyces coelicolor GlgEI (Sco GlgEI-V279S) was made to better emulate the Mtb GlgE M1P binding site. The structure of Sco GlgEI-V279S complexed with α-maltose-C-phosphonate (MCP), a non-hydrolyzable substrate analogue, was solved to 1.9 Å resolution, and the structure of Sco GlgEI-V279S complexed with 2,5-dideoxy-3-O-α-D-glucopyranosyl-2,5-imino-D-mannitol (DDGIM), an oxocarbenium mimic, was solved to 2.5 Å resolution. These structures detail important interactions that contribute to the inhibitory activity of these compounds, and provide information on future designs that may be exploited to improve upon these first generation GlgE inhibitors.

No MeSH data available.


Related in: MedlinePlus