ASSIGNMENT OF O-GLYCAN ATTACHMENT SITES TO THE HINGE-LIKE REGIONS OF HUMAN LYSOSOMAL MEMBRANE-GLYCOPROTEINS LAMP-1 AND LAMP-2
ASSIGNMENT OF O-GLYCAN ATTACHMENT SITES TO THE HINGE-LIKE REGIONS OF HUMAN LYSOSOMAL MEMBRANE-GLYCOPROTEINS LAMP-1 AND LAMP-2
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DOI：
10.1006/abbi.1993.1322
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发表时间：
1993-07-01
影响因子：
3.9
通讯作者：
FUKUDA, M
中科院分区：
文献类型：
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作者：
CARLSSON, SR;LYCKSELL, PO;FUKUDA, M
溶酶体膜糖蛋白LAMP-1和LAMP-2广泛地与N-连接和O-连接类型的各种不同的碳水化合物结构发生糖基化。在本文中，我们报道了从人慢性粒细胞白血病细胞中分离到的O-连接低聚糖特异性地定位于LAMP-1和LAMP-2的铰链区。在这两种糖蛋白中，硫代葡聚糖以簇状形式出现。在LAMP-1中，Thr-171、Thr-172、Ser-179、Ser-181和Ser-183完全糖基化，而Ser-169部分糖基化。在LAMP-2中，Ser-167、Thr-168、Thr-172、Thr-175、Thr-176、Thr-182和Thr-183有完全糖基化，Ser-179和Thr-181有部分糖基化，Thr-185可能也有部分糖基化。这些O-糖基化位点的氨基酸序列与先前报道的−1和+3位残基可能影响糖基化反应的报道一致。利用圆二色谱和核磁共振波谱对与LAMP-1的167-190位残基对应的合成肽进行了结构表征。结果表明，Pro-Richo-Gan受体区域不是典型的周期结构，而是不同于无规卷曲结构。然而，该多肽的圆二色谱与猪颌下无粘蛋白相似。在这一区域观察到了显著的构象变化，推测是由于(在核磁共振时间尺度上)几个脯氨酸残基的缓慢顺式转移。综上所述，这些结果强烈地表明，铰链区没有显示出任何典型的有序结构。因此，葡聚糖的存在可能保护这一区域不受腔内溶酶体蛋白酶的影响。
The lysosomal membrane glycoproteins lamp-1 and lamp-2 are extensively glycosylated with a variety of different carbohydrate structures of both N-linked and O-linked type. In the present paper, we report the localization of O-linked oligosaccharides exclusively to the hinge-like regions of lamp-1 and lamp-2 isolated from human chronic myelogenous leukemia cells. In both glycoproteins, theO-glycans appear in clusters. In lamp-1, Thr-171, Thr-172, Ser-179, Ser-181, and Ser-183 were fully glycosylated, whereas Ser-169 was partially glycosylated. In lamp-2, complete glycosylation was found at Ser-167, Thr-168, Thr-172, Thr-175, Thr-176, Thr-182, and Thr-183, and partial glycosylation at Ser-179 and Thr-181, and possibly also at Thr-185. The amino acid sequences of these O-glycosylation sites are consistent with the previous reports that residues at positions −1 and +3 may influence the glycosylation reaction. Circular dichroism and nuclear magnetic resonance spectroscopy was used for the structural characterization of a synthetic peptide corresponding to residues 167 to 190 of lamp-1. The results indicated that the proline-richO-glycan acceptor region does not adopt any typical periodic structure but differs from random-coil structure. The circular dichroism spectrum of the peptide is, however, similar to that of porcine submaxillary apomucin. A significant conformational variability was observed in this region, presumably due to a slow (on the nuclear magnetic resonance time scale)cis-transisomerization of several proline residues. These results, taken together, strongly suggest that a hinge region does not display any typical ordered structure. The presence ofO-glycans thus likely protects this region from intralumenal lysosomal proteases.