Dissection of protein-protein interaction and CDK4 inhibition in the oncogenic versus tumor suppressing functions of gankyrin and P16

JOURNAL OF MOLECULAR BIOLOGY

卷:373

Article

Mahajan, Anjali ; Guo, Y. ; Yuan, Chunhua ; Weghorst, Christopher M. ; Tsai, Ming-Daw ; Li, Junan

关键词: p16;    gankyrin;    CDK4 binding;    protein/protein interactions;    ankyrin repeat;   

DOI  :  10.1016/j.jmb.2007.08.038

来源: Elsevier

【 摘 要 】

Protein-protein interactions usually involve a large number of residues; thus it is difficult to elucidate functional and structural roles of specific residues located in the interface. This problem is particularly challenging for ankyrin repeat proteins (ARs), which consist of linear arrays of small repeating units and play critical roles in almost every life process via protein-protein interactions, because the residues involved are discontinuously dispersed in both the ARs and their partners. Our previous studies showed that while both specific CDK4 inhibitor p16(INK4A) (P16) and p gankyrin bind to cyclin-dependent kinase 4 (CDK4) in similar fashion, only P16 inhibits the kinase activity of CDK4. While this could explain why P16 is a tumor suppressor and gankyrin is oncogenic, the structural basis of these contrasting properties was unknown. Here we show that a double mutant of gankyrin, L62H/179D, inhibits the kinase activity of CDK4, similar to P16, and such CDK4-inhibtory activity is associated with the 179D but not L62H mutation. In addition, mutations at 179 and L62 bring about a moderate decrease in the stability of gankyrin. Further structural and biophysical analyses suggest that the substitution of Ile79 with Asp leads to local conformational changes in loops I-III of gankyrin. Taken together, our results allow the dissection of the protein-protein binding and CDK4 inhibition functions of P16, show that the difference between tumor suppressing and oncogenic functions of P16 and gankyrin, respectively, mainly resides in a single residue, and provide structural insight to the contrasting biological functions of the two AR proteins. (C) 2007 Elsevier Ltd. All rights reserved.

【 授权许可】

Free