ZNF750是一种核转录因子，可以激活皮肤分化，并在多种癌症中发挥肿瘤抑制作用。不同寻常的是，ZNF750仅有一个锌指结构域，Z*，其氨基酸序列与CCHH家族共识差异明显。由于其序列差异，Z*被归类为退化的，假定已经失去了折叠所需的结合锌离子的能力。AlphaFold对Z*的结构预测的准确性较低。准确性较低的预测通常被认为是蛋白质本征无序区域的情况，即如果Z*无法结合Zn2+，则会发生这种情况。我们使用NMR和CD光谱技术展示了ZNF750的25-51片段，对应于Z*结构域，可以折叠成定义良好的反平行ββα三级结构，其与Zn2+的离解常数为pM级，并具有热稳定性>80°C。在三种备选的Zn2+配体集中，Z*使用CCHC而不是预期的CCHH配位基团。最后一个配体的转换维持了经典ZNF结构域的折叠拓扑结构和疏水核心。CCHC型ZNF通常与蛋白质相互作用相关联，这引发了ZNF750可能通过其他蛋白质与DNA相互作用而不是直接结合的可能性。Z*的结构为我们理解该结构域及其与癌症相关突变的功能提供了背景。我们预期目前被归类为退化的其他ZNF可能是类似Z*的CCHC型结构。© 2023 The Author(s).

ZNF750 is a nuclear transcription factor that activates skin differentiation and has tumor suppressor roles in several cancers. Unusually, ZNF750 has only a single zinc-finger (ZNF) domain, Z*, with an amino acid sequence that differs markedly from the CCHH family consensus. Because of its sequence differences Z* is classified as degenerate, presumed to have lost the ability to bind the zinc ion required for folding. AlphaFold predicts an irregular structure for Z* with low confidence. Low confidence predictions are often inferred to be intrinsically disordered regions of proteins, which would be the case if Z* did not bind Zn2+. We use NMR and CD spectroscopy to show that a 25-51 segment of ZNF750 corresponding to the Z* domain folds into a well-defined antiparallel ββα tertiary structure with a pM dissociation constant for Zn2+ and a thermal stability >80 °C. Of three alternative Zn2+ ligand sets, Z* uses a CCHC rather than the expected CCHH ligating motif. The switch in the last ligand maintains the folding topology and hydrophobic core of the classical ZNF motif. CCHC ZNFs are typically associated with protein-protein interactions, raising the possibility that ZNF750 interacts with DNA through other proteins rather than directly. The structure of Z* provides context for understanding the function of the domain and its cancer-associated mutations. We expect other ZNFs currently classified as degenerate could be CCHC-type structures like Z*.© 2023 The Author(s).