Structures ofDrosophila melanogasterRab2 and Rab3 bound to GMPPNP

Abstract

PDB references: Rab3, 4rkf; Rab2, 4rke Rab GTPases belong to the large family of Ras proteins. They act as key regulators of membrane organization and intracellular trafficking. Functionally, they act as switches. In the active GTP-bound form they can bind to effector proteins to facilitate the delivery of transport vesicles. Upon stimulation, the GTP is hydrolyzed and the Rab proteins undergo conformational changes in their switch regions. This study focuses on Rab2 and Rab3 from Drosophila melanogaster. Whereas Rab2 is involved in vesicle transport between the Golgi and the endoplasmatic reticulum, Rab3 is a key player in exocytosis, and in the synapse it is involved in the assembly of the presynaptic active zone. Here, highresolution crystal structures of Rab2 and Rab3 in complex with GMPPNP and Mg 2+ are presented. In the structure of Rab3 a modified cysteine residue is observed with an enigmatic electron density attached to its thiol function.

Presynaptic precursor vesicles originate from thetrans-Golgi network, promoted by the small GTPase RAB2

“…And, although of fundamental importance, remained our understanding of the cell biological origin and molecular mechanics of presynaptic precursor biogenesis fragmentary. We here provide evidence, that in an early step of precursor biogenesis synaptic proteins sort out of the secretory trans-Golgi through independent routes on early, small and tubular membranous vesicles, a process clearly regulated by the small Golgi-related and highly conserved GTPase RAB2 (Chan et al, 2011;Lardong et al, 2015;Liu and Storrie, 2012;Lorincz et al, 2017;Saraste, 2016;Tisdale and Balch, 1996).…”

Mutational Analysis of Rab3 Function for Controlling Active Zone Protein Composition at the Drosophila Neuromuscular Junction

“…To investigate the molecular mechanism by which Rab3 functions to control the protein composition of individual active zones we performed a mutational analysis of Drosophila Rab3. Rab3 is highly conserved between flies and rodents both in terms of amino acid sequence (78% sequence identity with mouse Rab3a [ 28 ]; Fig 1A ) and protein structure [ 29 ]. Previous studies have identified specific residues of rodent Rab3 required for its roles in the regulation of exocytosis and the trafficking of synaptic vesicles [ 28 , 30 – 34 ].…”

“… (A) Sequence alignment of Drosophila Rab3 with mouse Rab3a. Amino acid numbers and labels for secondary structures (green, β-strands; blue, α-helices) and switch regions (pink) are shown for Drosophila Rab3, as determined by crystal structure analysis of fly Rab3 [ 29 ]. CDR region labels (yellow) correspond to the RabCDRs identified in rodent Rab3 [ 34 ].…”

“…The main binding interface with which Rab3 interacts with its effectors includes two switch regions ( Fig 1A , pink). Switch I is comprised of residues in the α1β2 loop and extends into the β2 strand; Switch II begins near the end of the β3 strand and extends through the α2 helix and into the α2β4 loop [ 23 , 29 , 44 ]. The switch regions undergo conformational changes that are dependent on the state of the guanine nucleotide that is bound and thus determine the proteins that Rab3 binds in each state [ 17 , 45 ].…”

Structural and Biophysical Characterization of Rab5a from Leishmania Donovani

“…Structural biology of Rabs and their related regulators and effectors is largely unexplored for Leishmania. Although a number of crystal structures of Rab proteins from different organisms have been reported (29)(30)(31)(32)(33)(34)(35), no structure for any of the Rab proteins from Leishmania has been determined so far. Although conventional Rab5 effectors like EEA1, Rabex5, Rabaptin5, and Rabenosyn5 have been well characterized in mammalian cells, their homologs have not been identified in Leishmania (15).…”