Vps9, Rabex-5 and DSS4: proteins with weak but distinct nucleotide-exchange activities for Rab proteins

Esters, Heike, Alexandrov, Kirill, Iakovenko, Andrei, Ivanova, Tania, Thoma, Nicolas, Rybin, Vladimir, Zerial, Marino, Scheidig, Axel J. and Goody, Roger S. (2001) Vps9, Rabex-5 and DSS4: proteins with weak but distinct nucleotide-exchange activities for Rab proteins. Journal of Molecular Biology, 310 1: 141-156. doi:10.1006/jmbi.2001.4735

Author Esters, Heike
Alexandrov, Kirill
Iakovenko, Andrei
Ivanova, Tania
Thoma, Nicolas
Rybin, Vladimir
Zerial, Marino
Scheidig, Axel J.
Goody, Roger S.
Title Vps9, Rabex-5 and DSS4: proteins with weak but distinct nucleotide-exchange activities for Rab proteins
Journal name Journal of Molecular Biology   Check publisher's open access policy
ISSN 0022-2836
Publication date 2001-06-29
Sub-type Article (original research)
DOI 10.1006/jmbi.2001.4735
Open Access Status Not yet assessed
Volume 310
Issue 1
Start page 141
End page 156
Total pages 16
Place of publication London, United Kingdom
Publisher Academic Press
Language eng
Formatted abstract
The activities of three Rab-specific factors with GDP/GTP exchange activity, Vps9p, Rabex-5 and DSS4, with their cognate GTPases, Ypt51p, Rab5 and Ypt1p, have been analysed quantitatively. In contrast to other exchange factors examined and to DSS4, Vps9p, and by analogy probably Rabex-5, have considerably lower affinity than GDP to the respective GTPases. In keeping with this, they are relatively weak exchangers, with a maximal rate constant for GDP release from the ternary complex between exchange factor, GTPase and GDP of ca 0.01 s-1, which is several orders of magnitude lower than for other exchange factors examined. If interaction with these proteins is a mandatory aspect of the Rab cycle, this suggests that the overall rate of cycling might be controlled at this point of the cycle. Surprisingly, DSS4, which has the thermodynamic potential to displace GDP effectively from Ypt1p, also does this very slowly, again with a maximal rate constant of ca 0.01 s-1. An additional, and based on present knowledge, unique, feature of the Ypt1p.DSS4 complex, is that the association of GTP (or GDP) is more than 103-fold slower than to Ypt1p, thus leading to a long life-time of the binary complex between the two proteins, even at the high nucleotide concentrations that prevail in the cell. This leads to the conclusion that the protein-protein complex is likely to have an important biological significance in addition to its probable role in GTP/GDP exchange.
Keyword DSS4
Exchange factors
Rab proteins
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: Institute for Molecular Bioscience - Publications
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