McCoy M, Stavridi E S, Waterman J L, Wieczorek A M, Opella S J, Halazonetis T D
Departments of Molecular Genetics and Structural Biology, The Wistar Institute, Philadelphia, PA 19104-4268, USA.
EMBO J. 1997 Oct 15;16(20):6230-6. doi: 10.1093/emboj/16.20.6230.
The p53 tumor suppressor oligomerization domain, a dimer of two primary dimers, is an independently folding domain whose subunits consist of a beta-strand, a tight turn and an alpha-helix. To evaluate the effect of hydrophobic side-chains on three-dimensional structure, we substituted residues Phe341 and Leu344 in the alpha-helix with other hydrophobic amino acids. Substitutions that resulted in residue 341 having a smaller side-chain than residue 344 switched the stoichiometry of the domain from tetrameric to dimeric. The three-dimensional structure of one such dimer was determined by multidimensional NMR spectroscopy. When compared with the primary dimer of the wild-type p53 oligomerization domain, the mutant dimer showed a switch in alpha-helical packing from anti-parallel to parallel and rotation of the alpha-helices relative to the beta-strands. Hydrophobic side-chain size is therefore an important determinant of a protein fold.
p53肿瘤抑制蛋白寡聚化结构域是由两个初级二聚体组成的二聚体，是一个独立折叠的结构域，其亚基由一条β链、一个紧密转角和一个α螺旋组成。为了评估疏水侧链对三维结构的影响，我们用其他疏水氨基酸取代了α螺旋中的苯丙氨酸341和亮氨酸344残基。导致341位残基的侧链比344位残基小的取代作用，使该结构域的化学计量从四聚体转变为二聚体。通过多维核磁共振光谱确定了其中一个这样的二聚体的三维结构。与野生型p53寡聚化结构域的初级二聚体相比，突变二聚体显示α螺旋堆积从反平行转变为平行，并且α螺旋相对于β链发生了旋转。因此，疏水侧链大小是蛋白质折叠的一个重要决定因素。
