Novel oligosaccharide side chains of the collagen-like region of BclA, the major glycoprotein of the Bacillus anthracis exosporium
Novel oligosaccharide side chains of the collagen-like region of BclA, the major glycoprotein of the Bacillus anthracis exosporium
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DOI：
10.1074/jbc.m401613200
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发表时间：
2004-07-23
影响因子：
4.8
通讯作者：
Turnbough, CL
中科院分区：
文献类型：
--
作者：
Daubenspeck, JM;Zeng, HD;Turnbough, CL
炭疽芽孢杆菌的孢子是炭疽病的病原体，它被一个突出的松散的层包围着，称为外孢壁。外孢壁由基底层和外部毛状绒毛组成。绒毛的细丝由称为BclA的高免疫原性糖蛋白组成，其具有长的中央胶原样区域，该区域具有多个XXG重复。大多数三联体重复序列是PTG，并且几乎所有三联体重复序列都含有苏氨酸残基，为O-糖基化提供了多个潜在位点。在这项研究中，我们证明了两个O-连接的寡糖，715-Da的四糖和324-Da的二糖，从孢子和孢子外壁相关的BclA肼解释放。每个寡糖可能通过GalNAc接头连接至BclA，GalNAc接头在寡糖释放期间丢失。我们发现四糖的多个拷贝连接到BclA的胶原样区域，而二糖可能连接在该区域之外。使用NMR、质谱和其它分析技术，我们确定该四糖的结构为2-O-甲基-4-（3-羟基-3-甲基丁酰胺基）-4，6-双脱氧-β-D-吡喃葡萄糖基-（1-> 3）-α-L-吡喃鼠李糖基-（1->3）-α-L-吡喃鼠李糖基-（1->2）-L-吡喃鼠李糖。以前未描述的非还原性末端糖（即2-O-甲基-4-（3-羟基-3-甲基丁酰胺基）-4，6-双脱氧-D-葡萄糖）被赋予俗名anthrose。在蜡状芽孢杆菌和苏云金芽孢杆菌的孢子中均未发现Anthrose，这两种芽孢杆菌在遗传学上与B最为相似。炭疽病因此，蒽糖可能是有用的物种特异性检测的B。炭疽孢子或作为治疗干预的新靶点。
Spores of Bacillus anthracis, the causative agent of anthrax, are enclosed by a prominent loose fitting layer called the exosporium. The exosporium consists of a basal layer and an external hairlike nap. The filaments of the nap are composed of a highly immunogenic glycoprotein called BclA, which has a long, central collagen-like region with multiple XXG repeats. Most of the triplet repeats are PTG, and nearly all of the triplet repeats contain a threonine residue, providing multiple potential sites for O-glycosylation. In this study, we demonstrated that two O-linked oligosaccharides, a 715-Da tetrasaccharide and a 324-Da disaccharide, are released from spore- and exosporium-associated BclA by hydrazinolysis. Each oligosaccharide is probably attached to BclA through a GalNAc linker, which was lost during oligosaccharide release. We found that multiple copies of the tetrasaccharide are linked to the collagen-like region of BclA, whereas the disaccharide may be attached outside of this region. Using NMR, mass spectrometry, and other analytical techniques, we determined that the structure of the tetrasaccharide is 2-O-methyl-4-(3-hydroxy-3-methylbutamido)-4,6- dideoxy-beta-D-glucopyranosyl-(1-->3)-alpha-L-rhamnopyranosyl( 1-->3)-alpha-L-rhamnopyranosyl-(1-->2)-L- rhamnopyranose. The previously undescribed nonreducing terminal sugar ( i.e. 2-O-methyl-4-(3-hydroxy- 3-methylbutamido)-4,6-dideoxy-D-glucose) was given the trivial name anthrose. Anthrose was not found in spores of either Bacillus cereus or Bacillus thuringiensis, two species that are the most phylogenetically similar to B. anthracis. Thus, anthrose may be useful for species-specific detection of B. anthracis spores or as a new target for therapeutic intervention.