The crystal structure of gankyrin, an oncoprotein found in complexes with cyclin-dependent kinase 4, a 19 S proteasomal ATPase regulator, and the tumor suppressors Rb and p53.
Gankyrin is a 25-kDa hepatocellular carcinoma-associated protein that mediates protein-protein interactions in cell cycle control and protein degradation. It has been reported to form complexes with cyclin-dependent kinase 4, retinoblastoma protein, the S6b ATPase subunit of the 19 S regulator of the 26 S proteasome, and Mdm2, an E3 ubiquitin ligase involved in p53 degradation. It is the first protein described to bind both to the 26 S proteasome and to proteins in other complexes containing cyclin-dependent kinase(s) and p53 ubiquitylating activities, thus providing a mechanism for delivering cell cycle regulating machinery and ubiquitylated substrates to the proteasome for degradation. Gankyrin contains a 33-residue motif known as the ankyrin repeat that occurs five and a half to six times in the sequence. As a step toward understanding gankyrin interactions with its protein partners we have determined its three-dimensional crystal structure to 2.0-A resolution. It reveals that the entire 226-residue gankyrin polypeptide folds into seven ankyrin repeat elements. The ankyrin repeats, consisting of an antiparallel beta-hairpin followed by a perpendicularly oriented helix-loop-helix, pack side-by-side, creating an extended curved structure with a groove running across the long concave surface. Comparison with the structures of other ankyrin repeat proteins suggests that interactions with partner proteins are mediated by residues situated on this concave surface.
Structural Biology Laboratory, University of York, York YO10 5YW, United Kingdom.
Szymon
S
Krzywda
Andrzej M
AM
Brzozowski
Hiroaki
H
Higashitsuji
Jun
J
Fujita
Rebecca
R
Welchman
Simon
S
Dawson
R John
RJ
Mayer
Anthony J
AJ
Wilkinson
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D045744:Cell Line, Tumor; D018360:Crystallography, X-Ray; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases / Q000737:chemistry* / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D004583:Electrons; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000378:metabolism*; D015513:Oncogene Proteins / Q000737:chemistry*; D010447:Peptide Hydrolases / Q000378:metabolism; D010455:Peptides / Q000737:chemistry; D010957:Plasmids / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex; D011487:Protein Conformation; D017510:Protein Folding; D011518:Proto-Oncogene Proteins; D016160:Retinoblastoma Protein / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
D009097:Multienzyme Complexes; D015513:Oncogene Proteins; C403591:PSMD10 protein, human; D010455:Peptides; D011518:Proto-Oncogene Proteins; D016160:Retinoblastoma Protein; D016159:Tumor Suppressor Protein p53; C495900:CDK4 protein, human; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases; D010447:Peptide Hydrolases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease