PDBsum entry: 2pz1

Signaling protein

PDB id: 2pz1

Contents

Protein chain

408 a.a. *

Waters ×100

* Residue conservation analysis

PDB id:

2pz1

Name:

Signaling protein

Title:

Crystal structure of auto-inhibited asef

Structure:

Rho guanine nucleotide exchange factor 4. Chain: a. Synonym: apc-stimulated guanine nucleotide exchange factor, engineered: yes

Source:

Homo sapiens. Human. Organism_taxid: 9606. Gene: arhgef4, kiaa1112. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

2.25Å R-factor: 0.221 R-free: 0.279

Authors:

L.Betts,J.Sondek,K.L.Rossman

Key ref:

N.Mitin et al. (2007). Release of autoinhibition of ASEF by APC leads to CDC42 activation and tumor suppression. Nat Struct Biol, 14, 814-823. PubMed id: 17704816 DOI: 10.1038/nsmb1290

Date:

17-May-07 Release date: 21-Aug-07

Protein chain

Q9NR80  (ARHG4_HUMAN) -  Rho guanine nucleotide exchange factor 4

Seq: 690 a.a.

Struc: 408 a.a.

 Gene Ontology (GO) functional annotation 

• Cellular component: intracellular (1 term)
• Biological process: intracellular signal transduction (2 terms)
• Biochemical function: protein binding (3 terms)

DOI no: 10.1038/nsmb1290

Nat Struct Biol 14:814-823 (2007)

PubMed id: 17704816

Release of autoinhibition of ASEF by APC leads to CDC42 activation and tumor suppression.

N.Mitin, L.Betts, M.E.Yohe, C.J.Der, J.Sondek, K.L.Rossman.

ABSTRACT

Autoinhibition of the Rho guanine nucleotide exchange factor ASEF is relieved by interaction with the APC tumor suppressor. Here we show that binding of the armadillo repeats of APC to a 'core APC-binding' (CAB) motif within ASEF, or truncation of the SH3 domain of ASEF, relieves autoinhibition, allowing the specific activation of CDC42. Structural determination of autoinhibited ASEF reveals that the SH3 domain forms an extensive interface with the catalytic DH and PH domains to obstruct binding and activation of CDC42, and the CAB motif is positioned adjacent to the SH3 domain to facilitate activation by APC. In colorectal cancer cell lines, full-length, but not truncated, APC activates CDC42 in an ASEF-dependent manner to suppress anchorage-independent growth. We therefore propose a model in which ASEF acts as a tumor suppressor when activated by APC and inactivation of ASEF by mutation or APC truncation promotes tumorigenesis.

Selected figure(s)

Figure 5.
(a) Schematic representations of full-length and truncated human APC. Top, APC contains oligomerization domain (OD), armadillo-repeat domain (ARM), regions for -catenin binding (15-residue repeats) and downregulation (20-residue repeats), sequences for Axin binding (SAMP repeats), basic domain that interacts directly with microtubules (MT), and EB1-binding region for indirect association with MTs. Bottom, APC is often mutated within the mutational cluster region (MCR) in cancers, leading to truncated protein. APC 1061 is a truncated form of APC that results from a common germline mutation. (b) Activated ASEF and CDC42 induce similar ruffles in COS-7 cells.

Figure 6.
(a) Ribbon diagram of ASEF. The SH3 domain forms an extensive interface with the DH and PH domains. The core APC-binding motif within the ABR contains a small -helix ( CAB) that rests against the n-Src loop of the SH3 domain. Dashed line represents disordered linker region between the SH3 and DH domains. (b) Comparison of autoinhibited ASEF with collybistin bound to CDC42. The structure of the collybistin DH and PH domains bound to CDC42 (PDB 2DFK) was superimposed on the structure of ASEF by aligning their DH domains. In this conformation, the DH and PH domains of ASEF could not bind CDC42 owing to steric clash, and large conformational differences are evident between the inhibited (ASEF) and activated (collybistin) states. Dashed lines indicate sites of steric clash; S2 is switch 2 in CDC42.

The above figures are reprinted from an Open Access publication published by Macmillan Publishers Ltd: Nat Struct Biol (2007, 14, 814-823) copyright 2007.

Figures were selected by an automated process.