Structure and function of the nontoxic components of Clostridium botulinum progenitor toxins.

肉毒梭菌神经毒素（Mr. 150 kDa）与培养物或食物中的无毒成分结合，形成大的复合物，命名为12 S（300 kDa）、16 S（500 kDa）和19 S（900 kDa）祖毒素。A型菌株产生12 S、16 S和19 S三种毒素，B、C和D型菌株产生12 S和16 S两种毒素，E、F和G型菌株只产生一种毒素，E和F型菌株产生12 S毒素，G型菌株产生16毒素。12 S毒素由神经毒素和无血凝素（HA）活性的无毒组分组成，称为NTNH，16 S和19 S毒素是由12 S毒素与HA结合形成的。结果表明：（1）任何类型的HA都由53、33、22 -23和17 kDa四个亚组分组成，它们以1：2：1：1的比例缔合;（2）22- 2kDa亚组分由几种分子量略有不同的蛋白质组成; 关于我们 19 S和16 S毒素由相同的蛋白质组分组成。4）A、C、D型12 S毒素的NTNH在其N-末端区域有切割，在SDS-PAGE上被分成两部分，A、C、D、E、F型NTNH的N-末端区域的多重比对表明切割发生在包括短重复序列的区域，而仅产生12 S毒素的E型和F型则缺少该区域。12 S和16 S（和19 S）毒素存在于同一培养物中的原因可能是NTNH的加工过程。5）HA的红细胞受体因毒素种类不同而不同; A和B毒素结合中性脂质，而C和D毒素结合两种糖脂中的唾液酸（如GM 3和唾液酸副糖苷）和糖蛋白（如血型糖蛋白），6）在C型中，HA的四个亚组分中的HA-33和HA-53具有与红细胞的结合活性，7）HA在前体毒素与小肠上皮细胞的结合中起重要作用，与HA阴性毒素相比，HA阳性毒素在小肠中的吸收更有效。少

Clostridium botulinum neurotoxins (Mr.150kDa) associate with nontoxic components in the cultures or in the foods, and become large complexes designated 12S (300 kDa), 16S (500 kDa), and 19S (900 kDa) progenitor toxins. Type A strain produces three formes of toxins, 12S,16S,and 19S,and type B,C,and D produce two formes of toxins, 12S and16S.Types E,F and G produce only one type of toxin ; types E and F produce 12S toxin, and type G produces 16 toxin. The 12S toxin consists of a neurotoxin and a nontoxic component showing no hemagglutinin (HA) activity, described here as a NTNH.The 16S and 19S toxins are formed by conjugation of 12S toxin with HA.The structure of progenitor toxins was clarified by both genetic- and protein chemical- analyzes. The conclusions drawn are 1) any types of HAs consist of four subcomponents, 53,33,22-23, and 17 kDa, which associated in the ratio of 1 : 2 : 1 : 1,2) the 22-2 kDa subcomponent consists of several proteins having a slightly different Mr, 3) type A … More 19S and 16S toxins consist of the same protein components. It was postulated that the 19S toxin is a dimmer of the 16S toxin cross-linked by HA-33,4) the NTNHs of type A,C,and D 12S toxins have a cleavage on their N-terminal regions, and are separated into two parts on SDS-PAGE.A multiple alignment of N-terminal regions of the NTNHs of types A,C,D,E,and F demonstrated that the cleavage occurs in a region including a short repeat sequence, and that types E and F which produce only 12S toxin lack this region. It was thought that the processing in NTNH is the reason why the 12S and 16S (and 19S) toxins exist in the same culture, 5) the receptors of red blood cells for HA arre different depending on the types of toxins ; A and B toxins bind to neutral lipids, whereas C and D toxins bind to sialic acids in both glicolipids (such as GM3 and sialylparagloboside) and glycoproteins (such as glycophorin), 6) In type C,HA-33 and HA-53 out of four subcomponents of HA,have the binding activity to the erythrocytes, 7) HA plays an important role for the progenitor toxin to bind to the epithelial cells of small intestine, that leads to efficient absorption of the HA-positive toxins is small intestine s compared with the HA-negative toxin. Less