The HPV16 E7 Viral Oncoprotein Self-Assembles into Defined Spherical Oligomers
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- 作者：Leonardo G. Alonso ; Maria M. Garcí ; a-Alai ; Clara Smal ; Juan M. Centeno ; Rubé ; n Iacono ; Eduardo Castañ ; o ; Peter Gualfetti ; and Gonzalo de Prat-Gay
- 刊名：Biochemistry
- 出版年：2004
- 出版时间：March 30, 2004
- 年：2004
- 卷：43
- 期：12
- 页码：3310 - 3317
- 全文大小：177K
- 年卷期：v.43,no.12(March 30, 2004)
- ISSN：1520-4995
文摘
Despite the fact that E7 is a major transforming oncoprotein in papillomavirus, its structureand precise molecular mechanism of action remain puzzling to date. E7 proteins share sequence homologyand proteasome targeting properties of tumor suppressors with adenovirus E1A and SV40 T antigen, twoother paradigmatic oncoproteins from DNA tumor viruses. High-risk HPV16 E7, a nonglobular dimerwith some properties of intrinsically disordered proteins, is capable of undergoing pH-dependentconformational transitions that expose hydrophobic surfaces to the solvent. We found that treatment witha chelating agent produced a protein that can readily assemble into homogeneous spherical particles withan average molecular mass of 790 kDa and a diameter of 50 nm, as determined from dynamic lightscattering and electron microscopy. The protein undergoes a substantial conformational transition fromcoil to 
-sheet structure, with concomitant consolidation of tertiary structure as judged by circular dichroismand fluorescence. The assembly process is very slow, in agreement with a substantial energy barrier causedby structural rearrangements. The resulting particles are highly stable, cooperatively folded, and capableof binding both Congo Red and thioflavin T, reporters of repetitive -sheet structures similar to thosefound in amyloids, although no fibrillar or insoluble material was observed under our experimentalconditions.
-sheet structure, with concomitant consolidation of tertiary structure as judged by circular dichroismand fluorescence. The assembly process is very slow, in agreement with a substantial energy barrier causedby structural rearrangements. The resulting particles are highly stable, cooperatively folded, and capableof binding both Congo Red and thioflavin T, reporters of repetitive -sheet structures similar to thosefound in amyloids, although no fibrillar or insoluble material was observed under our experimentalconditions.