RA-GEF, a novel Rap1A guanine nucleotide exchange factor containing a Ras/Rap1A-associating domain, is conserved between nematode and humans.
A yeast two-hybrid screening for Ras-binding proteins in nematode Caenorhabditis elegans has identified a guanine nucleotide exchange factor (GEF) containing a Ras/Rap1A-associating (RA) domain, termed Ce-RA-GEF. Both Ce-RA-GEF and its human counterpart Hs-RA-GEF possessed a PSD-95/DlgA/ZO-1 (PDZ) domain and a Ras exchanger motif (REM) domain in addition to the RA and GEF domains. They also contained a region homologous to a cyclic nucleotide monophosphate-binding domain, which turned out to be incapable of binding cAMP or cGMP. Although the REM and GEF domains are conserved with other GEFs acting on Ras family small GTP-binding proteins, the RA and PDZ domains are unseen in any of them. Hs-RA-GEF exhibited not only a GTP-dependent binding activity to Rap1A at its RA domain but also an activity to stimulate GDP/GTP exchange of Rap1A both in vitro and in vivo at the segment containing its REM and GEF domains. However, it did not exhibit any binding or GEF activity toward Ras. On the other hand, Ce-RA-GEF associated with and stimulated GDP/GTP exchange of both Ras and Rap1A. These results indicate that Ce-RA-GEF and Hs-RA-GEF define a novel class of Rap1A GEF molecules, which are conserved through evolution.
Liao
Y
Y
Department of Physiology II, Kobe University School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan.
Kariya
K
K
Hu
C D
CD
Shibatohge
M
M
Goshima
M
M
Okada
T
T
Watari
Y
Y
Gao
X
X
Jin
T G
TG
Yamawaki-Kataoka
Y
Y
Kataoka
T
T
D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans / Q000737:chemistry*; D029742:Caenorhabditis elegans Proteins; D003001:Cloning, Molecular; D017124:Conserved Sequence; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins; D011485:Protein Binding; D017386:Sequence Homology, Amino Acid; D018411:Spodoptera; D020827:rap1 GTP-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D018631:ras Proteins / Q000737:chemistry* / Q000378:metabolism
D029742:Caenorhabditis elegans Proteins; D020662:Guanine Nucleotide Exchange Factors; D009419:Nerve Tissue Proteins; C403525:RAPGEF2 protein, human; C403523:pxf-1 protein, C elegans; D020827:rap1 GTP-Binding Proteins; D018631:ras Proteins