1M7X

The X-ray Crystallographic Structure of Branching Enzyme

Summary for 1M7X

• Entry DOI: 10.2210/pdb1m7x/pdb
• Descriptor: 1,4-alpha-glucan Branching Enzyme (2 entities in total)
• Functional Keywords: alpha/beta barrel, beta sandwich, transferase
• Biological source: Escherichia coli
• Total number of polymer chains: 4
• Total formula weight: 287180.94

Authors

Abad, M.C.,Binderup, K.,Rios-Steiner, J.,Arni, R.K.,Preiss, J.,Geiger, J.H. (deposition date: 2002-07-23, release date: 2002-09-18, Last modification date: 2024-05-22)

Primary citation

Abad, M.C.,Binderup, K.,Rios-Steiner, J.,Arni, R.K.,Preiss, J.,Geiger, J.H.
The X-ray crystallographic structure of Escherichia coli branching enzyme
J.Biol.Chem., 277:42164-42170, 2002

PubMed Abstract: Branching enzyme catalyzes the formation of alpha-1,6 branch points in either glycogen or starch. We report the 2.3-A crystal structure of glycogen branching enzyme from Escherichia coli. The enzyme consists of three major domains, an NH(2)-terminal seven-stranded beta-sandwich domain, a COOH-terminal domain, and a central alpha/beta-barrel domain containing the enzyme active site. While the central domain is similar to that of all the other amylase family enzymes, branching enzyme shares the structure of all three domains only with isoamylase. Oligosaccharide binding was modeled for branching enzyme using the enzyme-oligosaccharide complex structures of various alpha-amylases and cyclodextrin glucanotransferase and residues were implicated in oligosaccharide binding. While most of the oligosaccharides modeled well in the branching enzyme structure, an approximate 50 degrees rotation between two of the glucose units was required to avoid steric clashes with Trp(298) of branching enzyme. A similar rotation was observed in the mammalian alpha-amylase structure caused by an equivalent tryptophan residue in this structure. It appears that there are two binding modes for oligosaccharides in these structures depending on the identity and location of this aromatic residue.

PubMed: 12196524
DOI: 10.1074/jbc.M205746200

Experimental method

X-RAY DIFFRACTION (2.3 Å)