Dimerization of CtIP may stabilize in vivo interactions with the Retinoblastoma-pocket domain.
CtIP is a tumor suppressor that interacts with Retinoblastoma protein (Rb) to regulate the G1/S-phase transition of the cell cycle. Despite its large size (897 residues) CtIP has few known structured regions. Rather it contains several linear motifs that interact with known binding partners, including an LXCXE motif that binds the pocket domain of Rb-family proteins. This LXCXE motif lies at the C-terminus of the only known structured domain, an N-terminal coiled-coil dimerization domain (DD; residues 45-160). Yeast two-hybrid (Y2H) and GST-pulldown analyses showed that CtIP requires the LXCXE motif to bind the Rb-pocket. Although isothermal titration calorimetry data indicates that the LXCXE motif is the sole determinant of binding affinity for the Rb-pocket domain (K(A) approximately 10(6)M(-1)), Y2H data indicates that the DD is required to stabilize the interaction in vivo. Thus dimerization may increase the apparent stability of the proteins and/or the lifetime of the complexes.
Stokes
Philippa H
PH
School of Molecular and Microbial Biosciences, University of Sydney, NSW 2006, Australia.
Thompson
Lyndal S
LS
Marianayagam
Neelan J
NJ
Matthews
Jacqueline M
JM
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism*; D019281:Dimerization; D004706:Endodeoxyribonucleases; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D016160:Retinoblastoma Protein / Q000737:chemistry* / Q000378:metabolism*; D013329:Structure-Activity Relationship
D002352:Carrier Proteins; D009687:Nuclear Proteins; D016160:Retinoblastoma Protein; D004706:Endodeoxyribonucleases; C410741:RBBP8 protein, human