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From Proteopedia
X-ray structure of the small G protein Rab11a in complex with GDP and Pi
Structural highlights
FunctionRB11A_HUMAN The small GTPases Rab are key regulators of intracellular membrane trafficking, from the formation of transport vesicles to their fusion with membranes. Rabs cycle between an inactive GDP-bound form and an active GTP-bound form that is able to recruit to membranes different set of downstream effectors directly responsible for vesicle formation, movement, tethering and fusion. That Rab regulates endocytic recycling. Acts as a major regulator of membrane delivery during cytokinesis. Together with MYO5B and RAB8A participates in epithelial cell polarization. Together with RAB3IP, RAB8A, the exocyst complex, PARD3, PRKCI, ANXA2, CDC42 and DNMBP promotes transcytosis of PODXL to the apical membrane initiation sites (AMIS), apical surface formation and lumenogenesis. Together with MYO5B participates in CFTR trafficking to the plasma membrane and TF (Transferrin) recycling in nonpolarized cells. Required in a complex with MYO5B and RAB11FIP2 for the transport of NPC1L1 to the plasma membrane. Participates in the sorting and basolateral transport of CDH1 from the Golgi apparatus to the plasma membrane. Regulates the recycling of FCGRT (receptor of Fc region of monomeric Ig G) to basolateral membranes. May also play a role in melanosome transport and release from melanocytes.[1] [2] [3] [4] [5] [6] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedGTP hydrolysis by small GTP binding proteins of the Ras superfamily is a universal reaction that controls multiple cellular regulations. Its enzymic mechanism has been the subject of long-standing debates as to the existence/identity of the general base and the electronic nature of its transition state. Here we report the high-resolution crystal structure of a small GTP binding protein, Rab11, solved in complex with GDP and Pi. Unexpectedly, a Pi oxygen and the GDP-cleaved oxygen are located less than 2.5 A apart, suggesting that they share a proton, likely in the form of a low-barrier hydrogen bond. This implies that the gamma-phosphate of GTP was protonated; hence, that GTP acts as a general base. Furthermore, this interaction should establish at, and stabilize, the transition state. Altogether, we propose a revised model for the GTPase reaction that should reconcile earlier models into a unique substrate-assisted mechanism. Crystallographic evidence for substrate-assisted GTP hydrolysis by a small GTP binding protein.,Pasqualato S, Cherfils J Structure. 2005 Apr;13(4):533-40. PMID:15837192[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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