Structural basis for ubiquitin recognition and autoubiquitination by Rabex-5.
Rabex-5 is an exchange factor for Rab5, a master regulator of endosomal trafficking. Rabex-5 binds monoubiquitin, undergoes covalent ubiquitination and contains an intrinsic ubiquitin ligase activity, all of which require an N-terminal A20 zinc finger followed immediately by a helix. The structure of the N-terminal portion of Rabex-5 bound to ubiquitin at 2.5-A resolution shows that Rabex-5-ubiquitin interactions occur at two sites. The first site is a new type of ubiquitin-binding domain, an inverted ubiquitin-interacting motif, which binds with approximately 29-microM affinity to the canonical Ile44 hydrophobic patch on ubiquitin. The second is a diaromatic patch on the A20 zinc finger, which binds with approximately 22-microM affinity to a polar region centered on Asp58 of ubiquitin. The A20 zinc-finger diaromatic patch mediates ubiquitin-ligase activity by directly recruiting a ubiquitin-loaded ubiquitin-conjugating enzyme.
Lee
Sangho
S
Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, US National Institutes of Health (NIH), Bethesda, Maryland 20892, USA.
Tsai
Yien Che
YC
Mattera
Rafael
R
Smith
William J
WJ
Kostelansky
Michael S
MS
Weissman
Allan M
AM
Bonifacino
Juan S
JS
Hurley
James H
JH
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D002417:Cattle; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D004252:DNA Mutational Analysis; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D013816:Thermodynamics; D025801:Ubiquitin / Q000737:chemistry / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D016335:Zinc Fingers
D020662:Guanine Nucleotide Exchange Factors; D025801:Ubiquitin; D044767:Ubiquitin-Protein Ligases