PDBsum entry 1ryh

Hydrolase

PDB id: 1ryh

Contents

Protein chains

171 a.a. *

Ligands

GNP ×2

Metals

_MG ×2

Waters ×296

* Residue conservation analysis

PDB id:

1ryh

Name:

Hydrolase

Title:

Alternative splicing of rac1 generates rac1b, a self-activating gtpase

Structure:

Ras-related c3 botulinum toxin substrate 1 isoform rac1b. Chain: a, b. Fragment: residues 1-201. Synonym: rac1b. Engineered: yes

Source:

Homo sapiens. Human. Organism_taxid: 9606. Expressed in: escherichia coli. Expression_system_taxid: 562.

Biol. unit:

Dimer (from PQS)

Resolution:

1.75Å R-factor: 0.183 R-free: 0.219

Authors:

M.R.Ahmadian,D.Fiegen

Key ref:

D.Fiegen et al. (2004). Alternative splicing of Rac1 generates Rac1b, a self-activating GTPase. J Biol Chem, 279, 4743-4749. PubMed id: 14625275 DOI: 10.1074/jbc.M310281200

Date:

22-Dec-03 Release date: 27-Jan-04

Protein chains

P63000  (RAC1_HUMAN) -  Ras-related C3 botulinum toxin substrate 1 from Homo sapiens

Seq: 192 a.a.

Struc: 171 a.a.*

* PDB and UniProt seqs differ at 2 residue positions (black crosses)

Enzyme reactions

• Enzyme class: E.C.3.6.5.2 - small monomeric GTPase.
• Reaction: GTP + H2O = GDP + phosphate + H⁺

GTP + H2O = GDP (Bound ligand (Het Group name = GNP) matches with 81.82% similarity) + phosphate + H(+)

Molecule diagrams generated from .mol files obtained from the KEGG ftp site

reference

DOI no: 10.1074/jbc.M310281200

J Biol Chem 279:4743-4749 (2004)

PubMed id: 14625275

Alternative splicing of Rac1 generates Rac1b, a self-activating GTPase.

D.Fiegen, L.C.Haeusler, L.Blumenstein, U.Herbrand, R.Dvorsky, I.R.Vetter, M.R.Ahmadian.

ABSTRACT

Rac1b was recently identified in malignant colorectal tumors as an alternative splice variant of Rac1 containing a 19-amino acid insertion next to the switch II region. The structures of Rac1b in the GDP- and the GppNHp-bound forms, determined at a resolution of 1.75 A, reveal that the insertion induces an open switch I conformation and a highly mobile switch II. As a consequence, Rac1b has an accelerated GEF-independent GDP/GTP exchange and an impaired GTP hydrolysis, which is restored partially by GTPase-activating proteins. Interestingly, Rac1b is able to bind the GTPase-binding domain of PAK but not full-length PAK in a GTP-dependent manner, suggesting that the insertion does not completely abolish effector interaction. The presented study provides insights into the structural and biochemical mechanism of a self-activating GTPase.

Selected figure(s)

Figure 3.
FIG. 3. Quantitative measurement of the PAK-GBD interaction with Rac1 (A) and Rac1b (B). Dissociation of mantGppNHp from Rac1b was inhibited by increasing concentration of the PAK-GBD (2-50 µM). The observed rate constants were plotted against the concentration of the PAK-GBD to obtain equilibrium dissociation constants of 0.49 µM for Rac1 and 3.55 µM for Rac1b.

Figure 4.
FIG. 4. Comparison of the Rac1b structures with Rac1. Ribbon representation of Rac1b·GDP (purple) and Rac1b·GppNHp (red) were superimposed on the structure of Rac1·GppNHp (brown) (17). The switch II region of Rac1 is highlighted in orange. The nucleotide (GppNHp of Rac1b) and the Mg2+ ion are shown as ball-and-stick.

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2004, 279, 4743-4749) copyright 2004.

Figures were selected by an automated process.