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Crystal structure of glycogen debranching enzyme and insights into its catalysis and disease-causing mutations.

Zhai L, Feng L, Xia L, Yin H, Xiang S - Nat Commun (2016)

Bottom Line: These studies reveal that distinct domains in GDE catalyse sequential reactions in glycogen debranching, the mechanism of their catalysis and highly specific substrate recognition.The unique tertiary structure of GDE provides additional contacts to glycogen besides its active sites, and our biochemical experiments indicate that they mediate its recruitment to glycogen and regulate its activity.Combining the understanding of the GDE catalysis and functional characterizations of its disease-causing mutations provides molecular insights into GSDIII.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.

ABSTRACT
Glycogen is a branched glucose polymer and serves as an important energy store. Its debranching is a critical step in its mobilization. In animals and fungi, the 170‚ÄČkDa glycogen debranching enzyme (GDE) catalyses this reaction. GDE deficiencies in humans are associated with severe diseases collectively termed glycogen storage disease type III (GSDIII). We report crystal structures of GDE and its complex with oligosaccharides, and structure-guided mutagenesis and biochemical studies to assess the structural observations. These studies reveal that distinct domains in GDE catalyse sequential reactions in glycogen debranching, the mechanism of their catalysis and highly specific substrate recognition. The unique tertiary structure of GDE provides additional contacts to glycogen besides its active sites, and our biochemical experiments indicate that they mediate its recruitment to glycogen and regulate its activity. Combining the understanding of the GDE catalysis and functional characterizations of its disease-causing mutations provides molecular insights into GSDIII.

No MeSH data available.


Related in: MedlinePlus

Disease-causing mutations and sequence conservation of GDE.(a) Disease-causing mutations of GDE. Missense mutations found in GSDIII patients are mapped onto the CgGDE structure, and represented by black spheres. (b) GDE residue conservation. The CgGDE is shown in surface representation, and coloured according to the conservation of individual residues. Bound oligosaccharides are shown in stick representation with their carbon atoms in white.
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f7: Disease-causing mutations and sequence conservation of GDE.(a) Disease-causing mutations of GDE. Missense mutations found in GSDIII patients are mapped onto the CgGDE structure, and represented by black spheres. (b) GDE residue conservation. The CgGDE is shown in surface representation, and coloured according to the conservation of individual residues. Bound oligosaccharides are shown in stick representation with their carbon atoms in white.

Mentions: The CgGDE structure provides a basis to understand the disease-causing mutations associated with GSDIII. Mapping the reported missense mutations343536 on the CgGDE structure revealed that they are located either on domain GT or GC (Fig. 7a and Supplementary Table 2). A number of the mutations are located at their substrate-binding sites, and are expected to disrupt substrate recruitment. These mutations include R428K, R524H and H626R (the equivalent positions in CgGDE are Pro450, Arg533 and His669, Fig. 4c) in the GT domain, and R1147G in the GC domain mentioned above. Several mutations located near the substrate-binding sites, including D215N and N219D in the GT domain, and G1087R and C1515R in the GC domain, likely have similar effects. Additional mutations might disrupt the folding and/or stability of GDE, indirectly affecting its activity. Mutations of this kind include L400P, L620P, G655R and G1448R. Decreased protein stability has been associated with the G1448R mutation37.


Crystal structure of glycogen debranching enzyme and insights into its catalysis and disease-causing mutations.

Zhai L, Feng L, Xia L, Yin H, Xiang S - Nat Commun (2016)

Disease-causing mutations and sequence conservation of GDE.(a) Disease-causing mutations of GDE. Missense mutations found in GSDIII patients are mapped onto the CgGDE structure, and represented by black spheres. (b) GDE residue conservation. The CgGDE is shown in surface representation, and coloured according to the conservation of individual residues. Bound oligosaccharides are shown in stick representation with their carbon atoms in white.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4837477&req=5

f7: Disease-causing mutations and sequence conservation of GDE.(a) Disease-causing mutations of GDE. Missense mutations found in GSDIII patients are mapped onto the CgGDE structure, and represented by black spheres. (b) GDE residue conservation. The CgGDE is shown in surface representation, and coloured according to the conservation of individual residues. Bound oligosaccharides are shown in stick representation with their carbon atoms in white.
Mentions: The CgGDE structure provides a basis to understand the disease-causing mutations associated with GSDIII. Mapping the reported missense mutations343536 on the CgGDE structure revealed that they are located either on domain GT or GC (Fig. 7a and Supplementary Table 2). A number of the mutations are located at their substrate-binding sites, and are expected to disrupt substrate recruitment. These mutations include R428K, R524H and H626R (the equivalent positions in CgGDE are Pro450, Arg533 and His669, Fig. 4c) in the GT domain, and R1147G in the GC domain mentioned above. Several mutations located near the substrate-binding sites, including D215N and N219D in the GT domain, and G1087R and C1515R in the GC domain, likely have similar effects. Additional mutations might disrupt the folding and/or stability of GDE, indirectly affecting its activity. Mutations of this kind include L400P, L620P, G655R and G1448R. Decreased protein stability has been associated with the G1448R mutation37.

Bottom Line: These studies reveal that distinct domains in GDE catalyse sequential reactions in glycogen debranching, the mechanism of their catalysis and highly specific substrate recognition.The unique tertiary structure of GDE provides additional contacts to glycogen besides its active sites, and our biochemical experiments indicate that they mediate its recruitment to glycogen and regulate its activity.Combining the understanding of the GDE catalysis and functional characterizations of its disease-causing mutations provides molecular insights into GSDIII.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.

ABSTRACT
Glycogen is a branched glucose polymer and serves as an important energy store. Its debranching is a critical step in its mobilization. In animals and fungi, the 170‚ÄČkDa glycogen debranching enzyme (GDE) catalyses this reaction. GDE deficiencies in humans are associated with severe diseases collectively termed glycogen storage disease type III (GSDIII). We report crystal structures of GDE and its complex with oligosaccharides, and structure-guided mutagenesis and biochemical studies to assess the structural observations. These studies reveal that distinct domains in GDE catalyse sequential reactions in glycogen debranching, the mechanism of their catalysis and highly specific substrate recognition. The unique tertiary structure of GDE provides additional contacts to glycogen besides its active sites, and our biochemical experiments indicate that they mediate its recruitment to glycogen and regulate its activity. Combining the understanding of the GDE catalysis and functional characterizations of its disease-causing mutations provides molecular insights into GSDIII.

No MeSH data available.


Related in: MedlinePlus