PSI Structural Biology Knowledgebase

PSI | Structural Biology Knowledgebase
Header Icons
E-Collection

Related Articles
Families in Gene Neighborhoods
June 2015
Signaling: A Platform for Opposing Functions
May 2015
Nuclear Pore Complex: A Flexible Transporter
February 2015
Nuclear Pore Complex: Higher Resolution of Macromolecules
February 2015
Nuclear Pore Complex: Integrative Approach to Probe Nup133
February 2015
Piecing Together the Nuclear Pore Complex
February 2015
iTRAQing the Ubiquitinome
July 2014
CAAX Endoproteases
August 2013
The Immune System: A Strong Competitor
June 2013
The Immune System: Strand Swapping for T-Cell Inhibition
June 2013
PDZ Domains
April 2013
Protein Interaction Networks: Adding Structure to Protein Networks
April 2013
Protein Interaction Networks: Morph to Assemble
April 2013
Protein Interaction Networks: Reading Between the Lines
April 2013
Protein Interaction Networks: When the Sum Is Greater than the Parts
April 2013
Alpha-Catenin Connections
March 2013
Cytochrome Oxidase
November 2012
Bacterial Phosphotransferase System
October 2012
Solute Channels
September 2012
Budding ensemble
August 2012
The machines behind the spindle assembly checkpoint
June 2012
G Protein-Coupled Receptors
May 2012
Revealing the Nuclear Pore Complex
March 2012
Topping off the proteasome
March 2012
Anchoring's the way
February 2012
Reading out regioselectivity
December 2011
An effective and cooperative dimer
November 2011
PDZ domains: sometimes it takes two
November 2011
Raising a glass to GLIC
August 2011
A2A Adenosine Receptor
May 2011
A growing family
February 2011
FERM-ly bound
February 2011
CXCR4
January 2011
Guard cells pick up the SLAC
December 2010
Zinc Transporter ZntB
July 2010
Zinc Transporter ZntB
July 2010
Importance of extension for integrin
June 2010
Spot protein-protein interactions… fast
March 2010
Alg13 Subunit of N-Acetylglucosamine Transferase
February 2010
Urea transporter
February 2010
Two-component signaling
December 2009
ABA receptor...this time for real?
November 2009
Network coverage
November 2009
Get3 into the groove
October 2009
Guanine Nucleotide Exchange Factor Vav1 and Rho GTPase Rac1
October 2009
GPCR subunits: Separate but not equal
September 2009
Proofreading RNA
July 2009
Ribonuclease and Ribonuclease Inhibitor
April 2009
The elusive helicase
April 2009
Click for cancer-protein interactions
December 2008

Research Themes Protein-protein interactions

Reading out regioselectivity

SBKB [doi:10.1038/sbkb.2011.52]
Featured Article - December 2011
Short description: The structures of four glycosyltransferases operating within a single biosynthetic pathway point to conserved and divergent mechanisms for controlling the regioselective addition of sugar donors, with implications for glycosyltransferase engineering.

Glycosyltransferase structures define the path for calicheamicin biosynthesis. Reprinted with permission from Proc. Natl. Acad. Sci. USA 1

Engineering glycosyltransferases to accommodate sugar analogs offers opportunities to broaden or alter the utility of an antibacterial or anticancer agent. However, the diversity of both natural product scaffolds and glycan donors used by glycosyltransferases has stymied the development of general rules for enzyme function and redesign strategies. Towards that end, Phillips, Thorson and colleagues (PSI CESG) now report four glycosyltransferase structures that highlight commonalities and differences determining sugar recognition and regioselective activity.

In calicheamicin biosynthesis, four glycosyltransferases are responsible for synthesizing a branched trisaccharide extending from the enediyne scaffold (performed by CalG3, CalG2 and CalG4) and decorating an aromatic group appended to the disaccharide (CalG1). Thus, each enzyme works on the same core molecule, but must attach a carbohydrate to different positions.

The new structures include CalG1, CalG2, and CalG3 with substrates and/or products as well as apo CalG4, which was used to predict the bound structure. Analysis of these structures points to conserved features in binding to the enediyne scaffold (with CalG1 providing some exceptions), including aromatic residues that contact the enediyne itself, a hydrophobic pocket postulated to protect an unusual methylated trisulfide group, and hydrogen bonding to a partner with unused hydroxyl groups. Additionally, a His residue is poised to play the major catalytic role, except in CalG2, which may use a Thr to catalyze the carbohydrate attachment to the more reactive hydroxylamine substrate.

A comparison of the structures identifies three ways in which the proteins diverge to control the reaction product. The first mechanism, using a short or long helix adjacent to the active site, yields different architectures within the protein as a whole to create different active sites. The second mechanism, reflecting a continuous or bent helix near the active site, changes the size of the active site. Finally, the different placement of the catalytic residue, as in CalG2, offers an alternative way of reshaping the reaction without substantial remodeling.

Overall, the combined analysis across four biosynthetically linked structures provides new insights that will shape our understanding of these interesting enzymes and the molecules they produce.

Catherine Goodman

References

  1. A. Chang et al. Complete set of glycosyltransferase structures in the calicheamicin biosynthetic pathway reveals the origin of regiospecificity.
    Proc. Natl. Acad. Sci. 108, 17649-17654 (2011). doi:10.1073/pnas.1108484108

Structural Biology Knowledgebase ISSN: 1758-1338
Funded by a grant from the National Institute of General Medical Sciences of the National Institutes of Health