Crystal structure of the ubiquitin binding domains of rabex-5 reveals two modes of interaction with ubiquitin.
The interaction between ubiquitinated proteins and intracellular proteins harboring ubiquitin binding domains (UBDs) is critical to a multitude of cellular processes. Here, we report that Rabex-5, a guanine nucleotide exchange factor for Rab5, binds to Ub through two independent UBDs. These UBDs determine a number of properties of Rabex-5, including its coupled monoubiquitination and interaction in vivo with ubiquitinated EGFRs. Structural and biochemical characterization of the UBDs of Rabex-5 revealed that one of them (MIU, motif interacting with ubiquitin) binds to Ub with modes superimposable to those of the UIM (ubiquitin-interacting motif):Ub interaction, although in the opposite orientation. The other UBD, RUZ (Rabex-5 ubiquitin binding zinc finger) binds to a surface of Ub centered on Asp58(Ub) and distinct from the "canonical" Ile44(Ub)-based surface. The two binding surfaces allow Ub to interact simultaneously with different UBDs, thus opening new perspectives in Ub-mediated signaling.
Penengo
Lorenza
L
IFOM, the FIRC Institute for Molecular Oncology Foundation, Via Adamello 16, 20139 Milan, Italy.
Mapelli
Marina
M
Murachelli
Andrea G
AG
Confalonieri
Stefano
S
Magri
Laura
L
Musacchio
Andrea
A
Di Fiore
Pier Paolo
PP
Polo
Simona
S
Schneider
Thomas R
TR
D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D004815:Epidermal Growth Factor / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D025801:Ubiquitin / Q000378:metabolism*
D020662:Guanine Nucleotide Exchange Factors; D046912:Multiprotein Complexes; C108382:RABGEF1 protein, human; D025801:Ubiquitin; D004815:Epidermal Growth Factor