4yon
From Proteopedia
P-Rex1:Rac1 complex
Structural highlights
Function[PREX1_HUMAN] Functions as a RAC guanine nucleotide exchange factor (GEF), which activates the Rac proteins by exchanging bound GDP for free GTP. Its activity is synergistically activated by phosphatidylinositol 3,4,5-trisphosphate and the beta gamma subunits of heterotrimeric G protein. May function downstream of heterotrimeric G proteins in neutrophils. [RAC1_HUMAN] Plasma membrane-associated small GTPase which cycles between active GTP-bound and inactive GDP-bound states. In its active state, binds to a variety of effector proteins to regulate cellular responses such as secretory processes, phagocytosis of apoptotic cells, epithelial cell polarization and growth-factor induced formation of membrane ruffles. Rac1 p21/rho GDI heterodimer is the active component of the cytosolic factor sigma 1, which is involved in stimulation of the NADPH oxidase activity in macrophages (By similarity). Essential for the SPATA13-mediated regulation of cell migration and adhesion assembly and disassembly. Stimulates PKN2 kinase activity. In concert with RAB7A, plays a role in regulating the formation of RBs (ruffled borders) in osteoclasts. In glioma cells, promotes cell migration and invasion.[1] [2] [3] [4] [5] Isoform B has an accelerated GEF-independent GDP/GTP exchange and an impaired GTP hydrolysis, which is restored partially by GTPase-activating proteins. It is able to bind to 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.[6] [7] [8] [9] [10] Publication Abstract from PubMedThe P-Rex (phosphatidylinositol(3,4,5)-trisphosphate (PIP3)-dependent Rac exchanger) family (P-Rex1 and P-Rex2) of Rho guanine nucleotide exchange factors (Rho GEFs) activate Rac GTPases to regulate cell migration, invasion and metastasis in several human cancers. The family is unique among Rho GEFs as their activity is regulated by the synergistic binding of PIP3 and Gbetagamma at the plasma membrane. However, the molecular mechanism of this family of multi-domain proteins remains unclear. We report the 1.95 A crystal structure of the catalytic P-Rex1 DH-PH tandem domain in complex with its cognate GTPase, Rac1 (Ras-related C3 botulinum toxin substrate-1). Mutations in the P-Rex1:Rac1 interface reveal a critical role of this complex in signaling downstream of receptor tyrosine kinases and G protein-coupled receptors. Structural data indicate the PIP3/Gbetagamma binding sites are on the opposite surface and markedly removed from the Rac1 interface, supporting a model whereby P-Rex1 binding to PIP3 and/or Gbetagamma releases inhibitory C-terminal domains to expose the Rac1 binding site. The Phosphatidylinositol (3,4,5)-trisphosphate-dependent Rac Exchanger 1:Ras-related C3 Botulinum Toxin Substrate 1 (P-Rex1:Rac1) Complex Reveals the Basis of Rac1 Activation in Breast Cancer Cells.,Lucato CM, Halls ML, Ooms LM, Liu HJ, Mitchell CA, Whisstock JC, Ellisdon AM J Biol Chem. 2015 Jun 24. pii: jbc.M115.660456. PMID:26112412[11] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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