Spalding T A, Birdsall N J, Curtis C A, Hulme E C
Division of Physical Biochemistry, Medical Research Council National Institute for Medical Research, London, United Kingdom.
J Biol Chem. 1994 Feb 11;269(6):4092-7.
Acetylcholine mustard (AChM) is an analogue of acetylcholine (ACh) in which the onium headgroup is replaced by a chemically reactive aziridinium moiety. AChM aziridinium has agonist activity, but, having bound, reacts with and blocks the muscarinic receptor (mAChR) binding site. Purified mAChRs from rat forebrain have been specifically labeled with [3H]AChM. The linkage formed is cleaved by hydroxylamine, is found within cyanogen bromide (CNBr) peptides with molecular masses of approximately 2.4 and 3.9 kDa, and is close to a disulfide-bonded cysteine. Edman degradation reveals a site of label attachment 26 residues C-terminal to a CNBr cleavage site. As in the case of the alkylating antagonist analogue [3H]propylbenzilylcholine mustard, these findings indicate that a conserved aspartic acid residue in transmembrane helix 3 of the mAChRs, corresponding to Asp-105 (m1 sequence), is the site of label attachment.
乙酰胆碱芥子气（AChM）是乙酰胆碱（ACh）的类似物，其中鎓头基被化学反应性氮丙啶部分取代。AChM氮丙啶具有激动剂活性，但结合后会与毒蕈碱受体（mAChR）结合位点发生反应并将其阻断。从大鼠前脑纯化的mAChRs已用[3H]AChM进行了特异性标记。形成的连接可被羟胺裂解，存在于分子量约为2.4和3.9 kDa的溴化氰（CNBr）肽中，且靠近二硫键连接的半胱氨酸。埃德曼降解揭示标记附着位点位于CNBr裂解位点C端26个残基处。与烷基化拮抗剂类似物[3H]丙基苯甲酰胆碱芥子气的情况一样，这些发现表明，mAChRs跨膜螺旋3中一个保守的天冬氨酸残基，对应于Asp-105（m1序列），是标记附着位点。
