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Rab-subfamily-specific regions of Ypt7p are structurally different from other RabGTPases
Alexandru-Tudor Constantinescu1, Alexey Rak, Kirill Alexandrov
1Abteilung für Physikalische Biochemie, Max-Planck Institut für Molekulare Physiologie, Otto-Hahn Strasse 11, 44227 Dortmund, Germany.
Abstract:
The GTPase Ypt7p from S. cerevisiae is involved in late endosome-to-vacuole transport and homotypic vacuole fusion. We present crystal structures of the GDP- and GppNHp-bound conformation of Ypt7p solved at 1.35 and 1.6 A resolution, respectively. Despite the similarity of the overall structure to other Ypt/Rab proteins, Ypt7p displays small but significant differences. The Ypt7p-specific residues Tyr33 and Tyr37 cause a difference in the main chain trace of the RabSF2 region and form a characteristic surface epitope. Ypt7p*GppNHp does not display the helix alpha2, characteristic of the Ras-superfamily, but instead possess an extended loop L4/L5. Due to insertions in loops L3 and L7, the neighboring RabSF1 and RabSF4 regions are different in their conformations to those of other Ypt/Rab proteins.
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