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Related Concept Videos

The JAK-STAT Signaling Pathway01:20

The JAK-STAT Signaling Pathway

Several cytokine receptors have tightly bound Janus kinase or JAK proteins attached at their cytosolic tail. Small signaling molecules such as cytokines, growth hormones, or prolactins bind to the cytokine receptors and initiate their dimerization. The dimerization brings the cytosolic JAKs together that trans-phosphorylate and activates each other. The activated JAKs now phosphorylate cytosolic tails of the cytokine receptors, which serve as binding sites for adaptor proteins such as  SH2...
MAPK Signaling Cascades01:07

MAPK Signaling Cascades

Mitogen-activated protein kinase, or MAPK pathway, activates three sequential kinases to regulate cellular responses such as proliferation, differentiation, survival, and apoptosis. The canonical MAPK pathway starts with a mitogen or growth factor binding to an RTK. The activated RTKs stimulate Ras, which recruits Raf or MAP3 Kinase (MAPKKK), the first kinase of the MAPK signaling cascade. Raf further phosphorylates and activates MEK or MAP2 Kinases (MAPKK), which in turn phosphorylates MAP...
PI3K/mTOR/AKT Signaling Pathway01:22

PI3K/mTOR/AKT Signaling Pathway

The mammalian target of rapamycin  (mTOR) is a serine/threonine kinase that regulates growth, proliferation, and cell survival in response to hormones, growth factors, or nutrient availability. This kinase exists in two structurally and functionally distinct forms: mTOR complex 1  (mTORC1) and mTOR complex 2  (mTORC2). The first form (mTORC1) is composed of a rapamycin-sensitive Raptor and proline-rich Akt substrate, PRAS40. In contrast,  mTORC2 consists of a rapamycin-insensitive companion...
Protein Kinases and Phosphatases02:54

Protein Kinases and Phosphatases

Proteins undergo chemical modifications that trigger changes in the charge, structure, and conformation of the proteins. Phosphorylation, acetylation, glycosylation, nitrosylation, ubiquitination, lipidation, methylation, and proteolysis are various protein modifications that regulate protein activity. Such modifications are usually enzyme-driven.
Protein kinases
Many proteins in the cell are regulated by phosphorylation, the addition of a phosphate group. A family of enzymes called kinases...
Interactions Between Signaling Pathways01:19

Interactions Between Signaling Pathways

Signaling cascades usually lack linearity. Multiple pathways interact and regulate one another, allowing cells to integrate and respond to diverse environmental stimuli.
Convergence and divergence, and cross-talk between signaling pathways
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cAMP-dependent Protein Kinase Pathways01:25

cAMP-dependent Protein Kinase Pathways

Cyclic Adenosine Monophosphate (cAMP) is an essential second messenger that activates protein kinase A (PKA) and regulates various biological processes. A single epinephrine molecule binds to GPCR and activates several heterotrimeric G proteins, each stimulating multiple adenylyl cyclase, amplifying the signal, and synthesizing large numbers of cAMP molecules. Small changes in cAMP concentration affect PKA activity. The binding of four cAMP molecules induces a conformational change in PKA,...

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Related Experiment Video

Updated: Jun 5, 2026

Assaying Protein Kinase Activity with Radiolabeled ATP
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Assaying Protein Kinase Activity with Radiolabeled ATP

Published on: May 26, 2017

Structural and functional studies indicate that the EPEC effector, EspG, directly binds p21-activated kinase.

Katherine L Germane1, Benjamin W Spiller

  • 1Department of Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States.

Biochemistry
|January 18, 2011
PubMed
Summary

Enteropathogenic Escherichia coli effector EspG, similar to Shigella VirA, binds to human p21-activated kinase (PAK). Mutations in EspG

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Published on: December 9, 2022

Area of Science:

  • Microbiology
  • Molecular Biology
  • Structural Biology

Background:

  • Bacterial pathogens utilize secreted effector proteins to manipulate host cell functions and evade immune responses.
  • Enteropathogenic Escherichia coli (EPEC) employs type III secretion systems to deliver effectors, including EspG, whose precise role remains unclear.
  • Virulence factors like Shigella's VirA share structural similarities with EPEC's EspG, suggesting potential functional overlap.

Purpose of the Study:

  • To elucidate the function and molecular mechanism of the EspG effector protein from enteropathogenic Escherichia coli.
  • To investigate the structural basis of EspG's interaction with host cell targets.
  • To determine if EspG interacts with p21-activated kinase (PAK) and characterize the binding interface.

Main Methods:

  • Comparative structural analysis of EspG and known virulence factors.
  • Biochemical assays to assess direct binding between purified EspG and human PAK.
  • Site-directed mutagenesis of conserved residues within the EspG surface pocket.
  • Assessment of the impact of mutations on EspG-PAK interaction.

Main Results:

  • EspG shares significant structural homology with the Shigella virulence factor VirA.
  • A large, conserved surface pocket was identified on the EspG structure.
  • EspG directly binds to the N-terminal inhibitory domain of human p21-activated kinase (PAK).
  • Mutations introduced into the conserved surface pocket of EspG abolished its binding to PAK.

Conclusions:

  • EspG functions as a virulence factor in EPEC by targeting and interacting with host cell machinery.
  • The interaction between EspG and PAK is mediated by a specific surface pocket, highlighting a structural determinant for effector function.
  • Understanding EspG-PAK interaction provides insights into bacterial subversion of host signaling pathways and potential therapeutic targets.