Lapuk V A, Tchukhrova A I, Katiashvili N M, Shmakova F V, Kaverzneva E D, Timofeev V P
N.D. Zelinsky Institute of Organic Chemistry, USSR Academy of Sciences, Moscow.
J Biomol Struct Dyn. 1990 Dec;8(3):709-20. doi: 10.1080/07391102.1990.10507837.
Demonstrated herein is the possibility of using the accessibility of tryptophan (Trp) residues in immunoglobulin M (IgM) upon modification with Koshland reagent (2-hydroxy-5-nitrobenzyl bromide) as an index of the conformational changeability of IgM. Of fourteen Trp's in the native IgM (per HL-region) only one appeared to be most accessible, evidently Trp312 in the mu-chain. Irreversible acidic and thermal conformational transitions in IgM increase the number of accessible Trp's approximately two-fold. Following partial enzymatic deglycosylation of IgM, deep scission of mannose in particular, all Trp's become inaccessible. Modification of the most accessible Trp increases 2-3 fold the number of tyrosine residues readily accessible upon nitration with tetranitromethane. Modification of four trp's using spin-label method data causes a sharp reduction of the mobility of the C mu 3 domain and a simultaneous decrease in the solubility of modified IgM.
本文证明了利用考什兰试剂（2-羟基-5-硝基苄基溴）修饰后免疫球蛋白M（IgM）中色氨酸（Trp）残基的可及性作为IgM构象可变性指标的可能性。天然IgM（每个重链区）中的14个Trp中只有一个似乎最易接近，显然是μ链中的Trp312。IgM中不可逆的酸性和热构象转变使可及Trp的数量增加约两倍。IgM进行部分酶促去糖基化后，尤其是甘露糖的深度断裂，所有Trp都变得不可及。修饰最易接近的Trp会使经四硝基甲烷硝化后易于接近的酪氨酸残基数量增加2至3倍。使用自旋标记法对四个Trp进行修饰的数据导致Cμ3结构域的流动性急剧降低，同时修饰后IgM的溶解度下降。
