NMR and molecular modeling studies on two glycopeptides from the carbohydrate-protein linkage region of connective tissue proteoglycans
NMR and molecular modeling studies on two glycopeptides from the carbohydrate-protein linkage region of connective tissue proteoglycans
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DOI：
10.1093/glycob/9.7.669
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发表时间：
1999-07-01
期刊：
影响因子：
4.3
通讯作者：
Krishna, NR
中科院分区：
文献类型：
--
作者：
Agrawal, PK;Jacquinet, JC;Krishna, NR
完整的H-1和C-13 NMR分配报告的两个糖肽代表结缔组织蛋白聚糖的糖蛋白键合区。这些糖肽是八糖六肽，Ser（Glc（p）A β（1->3）Gal（p）β（1-> 3）Gal（p）β（1->4）Xyl（p）β）-Gly-Ser-Gly-Ser（Glc（p）A β（1->3）Gal（p）β（1-> 3）Gal（p）β（1->4）Xyl（p）β）-Gly（1），和四糖二肽，Ser（Glc（p）A β（1->3）Gal（p）β（1->3）Gal（p）β（1->4）Xyl（p）β）-Gly（2），邻位偶合常数数据表明单糖残基采用C-4（1）椅式构象。距离几何/模拟退火计算，使用2D NOESY衍生的距离约束产生了一个单一的家庭的四糖部分的结构，与明确定义的interglycosidic键构象。糖苷C1 '-O 1键的phi扭转角显示出对-sc范围的严格偏好，而psi扭转角（O 1-Cn）显示出依赖于糖苷间键的位置（β（1->3）键为-ac，β（1->4）键为+ac）。糖肽键的主要构象是phi = -sc和psi = +ac。ROESY光谱中存在强d（alpha N）（i，i+1）NOE接触，一般不存在d（NN）（i，i+1）接触（除了弱Ser-5/Gly-6 d（NN）接触）和d（beta N）（i，i+1）接触（除了Ser-1/Gly-2），表明1的骨架主要处于伸展构象。将1的ROESY数据与从相同序列的未糖基化六肽（3）获得的数据进行比较，表明糖基化对六肽的骨架构象只有微小的影响。
Complete H-1 and C-13 NMR assignments are reported for two glycopeptides representing the carbohydrate-protein linkage region of connective tissue proteoglycans. These glycopeptides are the octasaccharide hexapeptide, Ser(Glc(p)A beta(1-->3) Gal(p)beta(1-->3)Gal(p)beta(1-->4)Xyl(p)beta)-Gly-Ser-Gly-Ser (Glc(p)A beta(1-->3)Gal(p)beta(1-->3)Gal(p)beta(1-->4)Xyl(p)beta)-Gly (1), and the tetrasaccharide dipeptide, Ser(Glc(p)A beta(1-->3)Gal(p)beta(1-->3)Gal(p)beta(1-->4)Xyl(p)beta)-Gly (2), The vicinal coupling constant data show that the monosaccharide residues adopt C-4(1) chair conformations. Distance geometry/simulated annealing calculations using 2D NOESY derived distance constraints yielded a single family of structures for the tetrasaccharide moiety, with well defined interglycosidic linkage conformations. The phi torsion angles of the glycosidic C1'-O1 bonds showed a strict preference for the -sc range whereas the psi torsion angles (O1-Cn) exhibited dependence upon the interglycosidic linkage position (-ac for beta(1-->3) linkage, +ac for beta(1-->4) linkage). The predominant conformation about the glycopeptide bond is phi = -sc and psi = +ac. The presence of strong d(alpha N) (i, i+1) NOE contacts, and the general absence of d(NN) (i, i+1) contacts (except for a weak Ser-5/Gly-6 d(NN) contact) and the d(beta N) (i, i+1) contacts (except for Ser-1/Gly-2) in the ROESY spectrum, suggest that the backbone for 1 is predominantly in an extended conformation. A comparison of the ROESY data for 1 with those obtained from the unglycosylated hexapeptide (3) of the same sequence suggests that glycosylation has only a marginal influence on the backbone conformation of the hexapeptide.