Isernia Carla, Bucci Enrico, Leone Marilisa, Zaccaro Laura, Di Lello Paola, Digilio Giuseppe, Esposito Sabrina, Saviano Michele, Di Blasio Benedetto, Pedone Carlo, Pedone Paolo V, Fattorusso Roberto
Dipartimento di Scienze Ambientali, Seconda Università di Napoli, 81100 Caserta, Italy.
Chembiochem. 2003 Mar 3;4(2-3):171-80. doi: 10.1002/cbic.200390028.
Zinc finger domains of the classical type represent the most abundant DNA binding domains in eukaryotic transcription factors. Plant proteins contain from one to four zinc finger domains, which are characterized by high conservation of the sequence QALGGH, shown to be critical for DNA-binding activity. The Arabidopsis thaliana SUPERMAN protein, which contains a single QALGGH zinc finger, is necessary for proper spatial development of reproductive floral tissues and has been shown to specifically bind to DNA. Here, we report the synthesis and UV and NMR spectroscopic structural characterization of a 37 amino acid SUPERMAN region complexed to a Zn(2+) ion (Zn-SUP37) and present the first high-resolution structure of a classical zinc finger domain from a plant protein. The NMR structure of the SUPERMAN zinc finger domain consists of a very well-defined betabetaalpha motif, typical of all other Cys(2)-His(2) zinc fingers structurally characterized. As a consequence, the highly conserved QALGGH sequence is located at the N terminus of the alpha helix. This region of the domain of animal zinc finger proteins consists of hypervariable residues that are responsible for recognizing the DNA bases. Therefore, we propose a peculiar DNA recognition code for the QALGGH zinc finger domain that includes all or some of the amino acid residues at positions -1, 2, and 3 (numbered relative to the N terminus of the helix) and possibly others at the C-terminal end of the recognition helix. This study further confirms that the zinc finger domain, though very simple, is an extremely versatile DNA binding motif.
经典类型的锌指结构域是真核转录因子中最丰富的DNA结合结构域。植物蛋白含有一到四个锌指结构域，其特征是序列QALGGH高度保守，该序列对DNA结合活性至关重要。拟南芥SUPERMAN蛋白含有一个单一的QALGGH锌指，对生殖花组织的正常空间发育是必需的，并且已被证明能特异性结合DNA。在此，我们报告了与Zn(2+)离子复合的37个氨基酸的SUPERMAN区域（Zn-SUP37）的合成以及紫外和核磁共振光谱结构表征，并展示了来自植物蛋白的经典锌指结构域的首个高分辨率结构。SUPERMAN锌指结构域的核磁共振结构由一个定义明确的betabetaalpha基序组成，这是所有其他已进行结构表征的Cys(2)-His(2)锌指的典型特征。因此，高度保守的QALGGH序列位于α螺旋的N端。动物锌指蛋白结构域的这一区域由负责识别DNA碱基的高度可变残基组成。因此，我们为QALGGH锌指结构域提出了一种独特的DNA识别密码，其中包括位置-1、2和3（相对于螺旋N端编号）的全部或部分氨基酸残基，以及识别螺旋C端可能的其他残基。这项研究进一步证实，锌指结构域虽然非常简单，但却是一种极其通用的DNA结合基序。
