Vaezeslami Soheila, Mathes Erika, Vasileiou Chrysoula, Borhan Babak, Geiger James H
Chemistry Department, Michigan State University, East Lansing, MI 48824-1322, USA.
J Mol Biol. 2006 Oct 27;363(3):687-701. doi: 10.1016/j.jmb.2006.08.059. Epub 2006 Aug 26.
CRABPII is a small, cytosolic protein that solubilizes and transfers retinoic acid (RA) to the nucleus while also enhancing its transcriptional activity. We have determined the first high-resolution structure of apo-wild type (WT) CRABPII at 1.35 A. Using three different data sets collected on apo-WT CRABPII we have shown that apo- and holo-CRABPII share very similar structures. Binding of RA appears to increase the overall rigidity of the structure, although the induced structural changes are not as pronounced as previously thought. The enhanced structural rigidity may be an important determinant for the enhanced nuclear localization of the RA-bound protein. Comparison of our apo-WT with a mutant apo-CRABPII structure shows that mutation of Arg111, a conserved residue of CRABPII and a key residue in RA binding, causes structural changes in the molecule. We further investigated the structural importance of conserved residues by determining the structure of the F15W mutant CRABPII (F15W-CRABPII). Our structures also demonstrate structural changes induced by crystal packing and show that a crystal can harbor demonstrative structural differences in the asymmetric unit.
细胞视黄酸结合蛋白II（CRABPII）是一种小分子胞质蛋白，它可溶解视黄酸（RA）并将其转运至细胞核，同时还能增强其转录活性。我们已确定了无配体野生型（WT）CRABPII在1.35埃分辨率下的首个高分辨率结构。利用在无配体WT CRABPII上收集的三个不同数据集，我们表明无配体和结合配体的CRABPII具有非常相似的结构。RA的结合似乎增加了结构的整体刚性，尽管诱导的结构变化并不像先前认为的那么明显。增强的结构刚性可能是结合RA的蛋白核定位增强的一个重要决定因素。将我们的无配体WT与突变型无配体CRABPII结构进行比较表明，CRABPII的保守残基Arg111（也是RA结合的关键残基）发生突变会导致分子结构发生变化。我们通过确定F15W突变型CRABPII（F15W-CRABPII）的结构，进一步研究了保守残基的结构重要性。我们的结构还展示了由晶体堆积诱导的结构变化，并表明晶体在不对称单元中可能存在显著的结构差异。
