crystal structure of human small GTPase Rab7(GTP)
[RAB7A_HUMAN] Defects in RAB7A are the cause of Charcot-Marie-Tooth disease type 2B (CMT2B) [MIM:600882]; also known as hereditary motor and sensory neuropathy II (HMSN2). CMT2B is a form of Charcot-Marie-Tooth disease, the most common inherited disorder of the peripheral nervous system. Charcot-Marie-Tooth disease is classified in two main groups on the basis of electrophysiologic properties and histopathology: primary peripheral demyelinating neuropathy or CMT1, and primary peripheral axonal neuropathy or CMT2. Neuropathies of the CMT2 group are characterized by signs of axonal regeneration in the absence of obvious myelin alterations, normal or slightly reduced nerve conduction velocities, and progressive distal muscle weakness and atrophy. CMT2B is clinically characterized by marked distal muscle weakness and a high frequency of foot ulcers, infections and amputations of the toes. CMT2B inheritance is autosomal dominant.   
[RAB7A_HUMAN] Key regulator in endo-lysosomal trafficking. Governs early-to-late endosomal maturation, microtubule minus-end as well as plus-end directed endosomal migration and positioning, and endosome-lysosome transport through different protein-protein interaction cascades. Plays a central role, not only in endosomal traffic, but also in many other cellular and physiological events, such as growth-factor-mediated cell signaling, nutrient-transportor mediated nutrient uptake, neurotrophin transport in the axons of neurons and lipid metabolism. Also involved in regulation of some specialized endosomal membrane trafficking, such as maturation of melanosomes, pathogen-induced phagosomes (or vacuoles) and autophagosomes. Plays a role in the maturation and acidification of phagosomes that engulf pathogens, such as S.aureus and M.tuberculosis. Plays a role in the fusion of phagosomes with lysosomes. Plays important roles in microbial pathogen infection and survival, as well as in participating in the life cycle of viruses. Microbial pathogens possess survival strategies governed by RAB7A, sometimes by employing RAB7A function (e.g. Salmonella) and sometimes by excluding RAB7A function (e.g. Mycobacterium). In concert with RAC1, plays a role in regulating the formation of RBs (ruffled borders) in osteoclasts. Controls the endosomal trafficking and neurite outgrowth signaling of NTRK1/TRKA. Regulates the endocytic trafficking of the EGF-EGFR complex by regulating its lysosomal degradation.   
Publication Abstract from PubMed
Rab7 regulates vesicle traffic from early to late endosomes, and from late endosomes to lysosomes. The crystal structure of Rab7-GTP in complex with the Rab7 binding domain of RILP reveals that Rab7 interacts with RILP specifically via two distinct areas, with the first one involving the switch and interswitch regions and the second one consisting of RabSF1 and RabSF4. Disruption of these interactions by mutations abrogates late endosomal/lysosomal targeting of Rab7 and RILP. The Rab7 binding domain of RILP forms a coiled-coil homodimer with two symmetric surfaces to interact with two separate Rab7-GTP molecules, forming a dyad configuration of Rab7-RILP(2)-Rab7. Mutations that disrupt RILP dimerization also abolish its interactions with Rab7-GTP and late endosomal/lysosomal targeting, suggesting that the dimeric form of RILP is a functional unit. Structural comparison suggests that the combined use of RabSF1 and RabSF4 with the switch regions may be a general mode of action for most Rab proteins in regulating membrane trafficking.
Structural basis for recruitment of RILP by small GTPase Rab7.,Wu M, Wang T, Loh E, Hong W, Song H EMBO J. 2005 Apr 20;24(8):1491-501. Epub 2005 Mar 31. PMID:15933719
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.