title: Crystal structure of Human ASB9-2 and substrate-recognition of CKB.
abstract: Human ankyrin repeat and suppressor of cytokine signaling box protein 9 (hASB9) is a specific substrate-recognition subunit of an elongin C-cullin-SOCS box E3 ubiquitin ligase complex. It recognizes its substrate, brain type creatine kinase (CKB), using the ankyrin repeat domain; and facilitates the polyubiquitination of CKB to mediate proteasomal degradation through the SOCS box domain. HASB9-2 is an isoform of hASB9 that contains one ankyrin repeat domain. In this study, the crystal structure of hASB9-2 is shown at 2.2-Å resolution using molecular replacement. Overall, hASB9-2 forms a slightly curved arch with a characteristic L-shaped cross-section. Amino acid substitution analysis based on docking experiments revealed that His103 and Phe107 in hASB9-2 are essential for binding to CKB. Analysis of truncation mutants demonstrated that the first six ankyrin repeats along with the N-terminal region of hASB9-2 contribute to the interaction with CKB.
authors.affiliation: State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, People's Republic of China.
authors.forename: Xiangwei
authors.initials: X
authors.lastname: Fei
authors.forename: Xing
authors.initials: X
authors.lastname: Gu
authors.forename: Shilong
authors.initials: S
authors.lastname: Fan
authors.forename: Zhenxing
authors.initials: Z
authors.lastname: Yang
authors.forename: Fan
authors.initials: F
authors.lastname: Li
authors.forename: Cheng
authors.initials: C
authors.lastname: Zhang
authors.forename: Weimin
authors.initials: W
authors.lastname: Gong
authors.forename: Yumin
authors.initials: Y
authors.lastname: Mao
authors.forename: Chaoneng
authors.initials: C
authors.lastname: Ji
mesh_terms: D000595:Amino Acid Sequence; D017089:Ankyrin Repeat; D001665:Binding Sites; D052276:Creatine Kinase, BB Form / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018360:Crystallography, X-Ray; D006801:Humans; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D016415:Sequence Alignment; D013379:Substrate Specificity; D050826:Suppressor of Cytokine Signaling Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: C540562:ASB9 protein, human; D050826:Suppressor of Cytokine Signaling Proteins; D052276:Creatine Kinase, BB Form