Loris R, Stas P P, Wyns L
Laboratorium voor Ultrastructuur, Vrije Universiteit Brussel, Sint-Genesius-Rode, Belgium.
J Biol Chem. 1994 Oct 28;269(43):26722-33.
An analysis of the water structure in the crystals of different legume lectins has been carried out. Protein hydration is found to be mainly dependent on the detailed local surface characteristics of the protein and will adapt upon the limited conformational changes that are the resultant of crystal packing forces and point mutations. Yet a significant portion of the water positions determined by x-ray crystallography appears to be conserved in all independent crystal structures of a given protein. Some of these waters are specific to this one specific protein, while others are conserved in crystal structures of homologous proteins as well. For those conserved waters, a clear structural role is often evident. Seven water sites were found to be completely conserved in all legume lectin crystal structures, independent of their degree of sequence homology or carbohydrate specificity. Of these, four waters are ligands to the manganese and calcium ions, and one water is located in the saccharide binding site interacting with a conserved Asp and Asn residue. Of the remaining two conserved waters, one of them stabilizes a beta-hairpin, while the other interacts with a beta-bulge structure of the back sheet.
对不同豆科植物凝集素晶体中的水结构进行了分析。发现蛋白质水合作用主要取决于蛋白质详细的局部表面特征，并会随着晶体堆积力和点突变导致的有限构象变化而调整。然而，通过X射线晶体学确定的水的位置中，很大一部分在给定蛋白质的所有独立晶体结构中似乎是保守的。其中一些水是这种特定蛋白质所特有的，而其他一些水在同源蛋白质的晶体结构中也保守。对于那些保守的水，其明确的结构作用往往很明显。在所有豆科植物凝集素晶体结构中发现有七个水位点完全保守，与它们的序列同源性程度或碳水化合物特异性无关。其中，四个水是锰离子和钙离子的配体，一个水位于糖结合位点，与一个保守的天冬氨酸和天冬酰胺残基相互作用。在其余两个保守的水中，其中一个稳定一个β-发夹结构，而另一个与后片的β-凸起结构相互作用。
