Mandal C, Basu S, Mandal C
Indian Institute of Chemical Biology, Calcutta.
Biochem J. 1989 Jan 1;257(1):65-71. doi: 10.1042/bj2570065.
We have purified a sialic acid-binding lectin, achatininH, in a single step by affinity chromatography, having high affinity for 9-O-acetylneuraminic acid. The physicochemical characterization of the interaction of achatininH with bivalent metal ions and sialic acid derivatives by the use of spectrofluorimetry, spectropolarimetry and precipitin reaction is reported. From fluorescence quenching studies the binding of Ca2+ (Ka = 251 +/- 9 M-1) and of Mn2+ (Ka = 86 +/- 5 M-1) was found to be weak, but their presence is absolutely necessary for sugar binding as well as biological activity. The nature and position of the substituent group play a very important role in the binding affinity. AchatininH shows a high affinity for 9-O-acetylneuraminic acid (Ka = 1.20 x 10(3) +/- 0.07 x 10(3) M-1) compared with that for the 4-O-acetyl derivative. In oligomers the binding strength increases in the order monosaccharide less than disaccharide less than trisaccharide. The binding affinity of achatininH for the disaccharide was found to reach a peak around pH 8. From c.d. spectral studies achatininH was found to have a high beta-sheet content (46%) and a low alpha-helix content (24%). From precipitin analysis at least one sugar-binding site on each of the 16 monomer subunits of the protein is indicated.
我们通过亲和色谱一步法纯化了一种唾液酸结合凝集素——玛瑙螺凝集素H（achatininH），它对9-O-乙酰神经氨酸具有高亲和力。本文报道了利用荧光光谱法、旋光光谱法和沉淀反应对玛瑙螺凝集素H与二价金属离子及唾液酸衍生物相互作用的物理化学特性研究。通过荧光猝灭研究发现，Ca2+（Ka = 251 ± 9 M-1）和Mn2+（Ka = 86 ± 5 M-1）的结合较弱，但它们的存在对于糖结合以及生物活性来说是绝对必要的。取代基的性质和位置在结合亲和力中起着非常重要的作用。与4-O-乙酰衍生物相比，玛瑙螺凝集素H对9-O-乙酰神经氨酸表现出高亲和力（Ka = 1.20×10(3) ± 0.07×10(3) M-1）。在寡聚物中，结合强度按单糖＜二糖＜三糖的顺序增加。发现玛瑙螺凝集素H对二糖的结合亲和力在pH 8左右达到峰值。通过圆二色光谱研究发现，玛瑙螺凝集素H具有高β-折叠含量（46%）和低α-螺旋含量（24%）。通过沉淀分析表明，该蛋白质的16个单体亚基中每个亚基上至少有一个糖结合位点。
