A glycosyltransferase with a length-controlling activity as a mechanism to regulate the size of polysaccharides

ANDRES E. CIOCCHINI; L. SOLEDAD GUIDOLIN; ADRIANA C. CASABUONO; ALICIA S. COUTO; NORA INON DE IANNINO; RODOLFO A. UGALDE

PNAS

National Academy of Sciences

Lugar: USA; Año: 2007 vol. 104 p. 16492 - 16497

0027-8424

Cyclic
-1,2-glucans (C
G) are osmolyte homopolysaccharides with a cyclic
-1,2-backbone of 17–25 glucose residues present in the periplasmic space of several bacteria. Initiation, elongation, and cyclization, the three distinctive reactions required for building the cyclic structure, are catalyzed by the same protein, the C
G synthase. The initiation activity catalyzes the transference of the first glucose from UDP-glucose to a yet-unidentified amino acid residue in the same protein. Elongation proceeds by the successive addition of glucose residues from UDP-glucose to the nonreducing end of the protein-linked
-1,2-oligosaccharide intermediate. Finally, the protein- linked intermediate is cyclized, and the cyclic glucan is released from the protein. These reactions do not explain, however, the mechanism by which the number of glucose residues in the cyclic structure is controlled. We now report that control of the degree of polymerization (DP) is carried out by a
-1,2-glucan phosphorylase present at the C
G synthase C-terminal domain. This last activity catalyzes the phosphorolysis of the
-1,2-glucosidic bond at the nonreducing end of the linear protein-linked intermediate, releasing glucose 1-phosphate. The DP is thus regulated by this ‘‘lengthcontrolling’’ phosphorylase activity. To our knowledge, this is the first description of a control of the DP of homopolysaccharides.
-1,2-glucans (C
G) are osmolyte homopolysaccharides with a cyclic
-1,2-backbone of 17–25 glucose residues present in the periplasmic space of several bacteria. Initiation, elongation, and cyclization, the three distinctive reactions required for building the cyclic structure, are catalyzed by the same protein, the C
G synthase. The initiation activity catalyzes the transference of the first glucose from UDP-glucose to a yet-unidentified amino acid residue in the same protein. Elongation proceeds by the successive addition of glucose residues from UDP-glucose to the nonreducing end of the protein-linked
-1,2-oligosaccharide intermediate. Finally, the protein- linked intermediate is cyclized, and the cyclic glucan is released from the protein. These reactions do not explain, however, the mechanism by which the number of glucose residues in the cyclic structure is controlled. We now report that control of the degree of polymerization (DP) is carried out by a
-1,2-glucan phosphorylase present at the C
G synthase C-terminal domain. This last activity catalyzes the phosphorolysis of the
-1,2-glucosidic bond at the nonreducing end of the linear protein-linked intermediate, releasing glucose 1-phosphate. The DP is thus regulated by this ‘‘lengthcontrolling’’ phosphorylase activity. To our knowledge, this is the first description of a control of the DP of homopolysaccharides.
-1,2-backbone of 17–25 glucose residues present in the periplasmic space of several bacteria. Initiation, elongation, and cyclization, the three distinctive reactions required for building the cyclic structure, are catalyzed by the same protein, the C
G synthase. The initiation activity catalyzes the transference of the first glucose from UDP-glucose to a yet-unidentified amino acid residue in the same protein. Elongation proceeds by the successive addition of glucose residues from UDP-glucose to the nonreducing end of the protein-linked
-1,2-oligosaccharide intermediate. Finally, the protein- linked intermediate is cyclized, and the cyclic glucan is released from the protein. These reactions do not explain, however, the mechanism by which the number of glucose residues in the cyclic structure is controlled. We now report that control of the degree of polymerization (DP) is carried out by a
-1,2-glucan phosphorylase present at the C
G synthase C-terminal domain. This last activity catalyzes the phosphorolysis of the
-1,2-glucosidic bond at the nonreducing end of the linear protein-linked intermediate, releasing glucose 1-phosphate. The DP is thus regulated by this ‘‘lengthcontrolling’’ phosphorylase activity. To our knowledge, this is the first description of a control of the DP of homopolysaccharides.
G synthase. The initiation activity catalyzes the transference of the first glucose from UDP-glucose to a yet-unidentified amino acid residue in the same protein. Elongation proceeds by the successive addition of glucose residues from UDP-glucose to the nonreducing end of the protein-linked
-1,2-oligosaccharide intermediate. Finally, the protein- linked intermediate is cyclized, and the cyclic glucan is released from the protein. These reactions do not explain, however, the mechanism by which the number of glucose residues in the cyclic structure is controlled. We now report that control of the degree of polymerization (DP) is carried out by a
-1,2-glucan phosphorylase present at the C
G synthase C-terminal domain. This last activity catalyzes the phosphorolysis of the
-1,2-glucosidic bond at the nonreducing end of the linear protein-linked intermediate, releasing glucose 1-phosphate. The DP is thus regulated by this ‘‘lengthcontrolling’’ phosphorylase activity. To our knowledge, this is the first description of a control of the DP of homopolysaccharides.
-1,2-oligosaccharide intermediate. Finally, the protein- linked intermediate is cyclized, and the cyclic glucan is released from the protein. These reactions do not explain, however, the mechanism by which the number of glucose residues in the cyclic structure is controlled. We now report that control of the degree of polymerization (DP) is carried out by a
-1,2-glucan phosphorylase present at the C
G synthase C-terminal domain. This last activity catalyzes the phosphorolysis of the
-1,2-glucosidic bond at the nonreducing end of the linear protein-linked intermediate, releasing glucose 1-phosphate. The DP is thus regulated by this ‘‘lengthcontrolling’’ phosphorylase activity. To our knowledge, this is the first description of a control of the DP of homopolysaccharides.
-1,2-glucan phosphorylase present at the C
G synthase C-terminal domain. This last activity catalyzes the phosphorolysis of the
-1,2-glucosidic bond at the nonreducing end of the linear protein-linked intermediate, releasing glucose 1-phosphate. The DP is thus regulated by this ‘‘lengthcontrolling’’ phosphorylase activity. To our knowledge, this is the first description of a control of the DP of homopolysaccharides.
G synthase C-terminal domain. This last activity catalyzes the phosphorolysis of the
-1,2-glucosidic bond at the nonreducing end of the linear protein-linked intermediate, releasing glucose 1-phosphate. The DP is thus regulated by this ‘‘lengthcontrolling’’ phosphorylase activity. To our knowledge, this is the first description of a control of the DP of homopolysaccharides.
-1,2-glucosidic bond at the nonreducing end of the linear protein-linked intermediate, releasing glucose 1-phosphate. The DP is thus regulated by this ‘‘lengthcontrolling’’ phosphorylase activity. To our knowledge, this is the first description of a control of the DP of homopolysaccharides.