PSI Structural Biology Knowledgebase

PSI | Structural Biology Knowledgebase
Header Icons
E-Collection

Related Articles
Design and Evolution: Molecular Sleuthing Reveals Drug Selectivity
June 2015
Families in Gene Neighborhoods
June 2015
Ryanodine Receptor
April 2015
CCR5 and HIV Infection
January 2015
Drug Targets: Bile Acids in Motion
September 2014
Drug Targets: S1R's Ligands and Partners
September 2014
P2Y Receptors and Blood Clotting
September 2014
Bacterial CDI Toxins
June 2014
Glucagon Receptor
April 2014
Viroporins
March 2014
Microbial Pathogenesis: Targeting Drug Resistance in Mycobacterium tuberculosis
February 2014
Design and Discovery: Virtual Drug Screening
January 2014
Cancer Networks: IFI16-mediated p53 Activation
November 2013
G Proteins and Cancer
November 2013
Drug Discovery: Antidepressant Potential of 6-NQ SERT Inhibitors
October 2013
Drug Discovery: Finding Druggable Targets
October 2013
Drug Discovery: Identifying Dynamic Networks by CONTACT
October 2013
Drug Discovery: Modeling NET Interactions
October 2013
Membrane Proteome: GPCR Substrate Recognition and Functional Selectivity
August 2013
Infectious Diseases: Determining the Essential Structome
May 2013
NDM-1 and Antibiotics
May 2013
Microbial Pathogenesis: Computational Epitope Prediction
January 2013
Microbial Pathogenesis: Influenza Inhibitor Screen
January 2013
Microbial Pathogenesis: Measles Virus Attachment
January 2013
Cytochrome Oxidase
November 2012
Membrane Proteome: The ABCs of Transport
November 2012
Bacterial Phosphotransferase System
October 2012
Regulatory insights
September 2012
Solute Channels
September 2012
Pocket changes
July 2012
Receptor bias
July 2012
Anthrax Stealth Siderophores
June 2012
G Protein-Coupled Receptors
May 2012
Substrate specificity sleuths
April 2012
Reading out regioselectivity
December 2011
Superbugs and Antibiotic Resistance
December 2011
Terminal activation
December 2011
A change to resistance
November 2011
Docking and rolling
October 2011
Breaking down the defenses
September 2011
A2A Adenosine Receptor
May 2011
Cell wall recycler
May 2011
Subtly different
March 2011
CXCR4
January 2011
Subtle shifts
January 2011
ABA receptor diversity
November 2010
COX inhibition: Naproxen by proxy
November 2010
Zinc Transporter ZntB
July 2010
Peptidoglycan binding: Calcium-free killing
June 2010
Treating sleeping sickness
May 2010
Bacterial spore kinase
April 2010
Antibiotics and Ribosome Function
March 2010
Safer Alzheimer's drugs?
March 2010
Anthrax evasion tactics
September 2009
GPCR subunits: Separate but not equal
September 2009
Antibiotic target
August 2009
Salicylic Acid Binding Protein 2
August 2009
Lysostaphin
July 2009
Tackling influenza
June 2009
Bacterial Leucine Transporter, LeuT
May 2009
Anthrax stealth molecule
March 2009
Drug targets to aim for
February 2009
High-energy storage system
February 2009
Transporter mechanism in sight
February 2009
Scavenger Decapping Enzyme DcpS
November 2008
Blocking AmtB
September 2008

Research Themes Drug discovery

Terminal activation

SBKB [doi:10.1038/sbkb.2011.51]
Featured Article - December 2011
Short description: The recent crystal structure of the human BIG2 Sec7 domain reveals a novel ARF-interacting motif that regulates ARF activation.

Model of human BIG2 Sec7 domain (PDB 3L8N, green) in a complex with ARF1 (cyan). The loop>J of BIG2 Sec7 domain is positioned close to the switch I (Sw. I) region of ARF1. Image courtesy of Elizabeth Sztul.

G proteins are key signaling molecules that serve as molecular switches by cycling between an inactive GDP-bound state and an active GTP-bound state. G proteins are activated by guanine nucleotide exchange factors (GEFs), which catalyze the exchange of GDP for GTP, and inactivated by GTPase activating proteins (GAPs), which catalyze the hydrolysis of GTP to GDP. Understanding the interplay between G proteins, GEFs, and GAPs is essential to discovering the intricate signaling pathways in the cell.

As part of the PSI:Biology's Community Outreach activities, Sztul and colleagues with collaborators from the PSI NESG have examined the activation of ADP-ribosylation factors (ARFs), a family of G proteins involved in membrane trafficking and intracellular signaling, by GEFs. ARF GEFs are characterized by a conserved Sec7 domain, which is responsible for ARF binding and for catalyzing the exchange of GDP for GTP. The authors determined the crystal structure of the Sec7 domain of the ARF GEF human BIG2 which, along with other Sec7 domain family members, is a target of the NESG Human Cancer Protein Interaction program. The structure, which is similar to structures of other Sec7 domains, reveals an elongated rod-shaped protein consisting of ten α-helices with a hydrophobic groove forming the ARF-binding interface. Upon modeling the ARF-Sec7 domain complex, the authors predicted a novel ARF-interacting motif in the C-terminus of the Sec7 domain located in the loop after helix J (loop>J).

The authors investigated the functional role of loop>J by mutating residues in loop>J from Sec7 domains of several ARF GEFs (BIG2, GBF1, and ARNO). Mutations in loop>J in BIG2 and GBF1 produced phenotypes similar to catalytically dead mutants in vivo, suggesting that loop>J is involved in catalyzing guanine nucleotide exchange. Pull-down and FRAP assays with BIG2, GBF1, and ARNO revealed that mutation of loop>J decreases ARF binding, resulting in a decrease in GDP to GTP exchange.

This is the first study to identify the role of loop>J in ARF GEFs in substrate recognition and catalysis. Understanding the interactions that lead to ARF activation could provide insight into the selectivity of ARF GEFs and aid in designing GEF-specific inhibitors.

Jennifer Cable

References

  1. J. Lowery et al. Novel C-terminal Motif within Sec7 Domain of Guanine Nucleotide Exchange Factors Regulates ADP-ribosylation Factor (ARF) Binding and Activation.
    J. Biol. Chem. 286, 36898-36906 (2011). doi:10.1074/jbc.M111.230631

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