Schuman Jason T, Grinstead Jeffrey S, Apostolopoulos Vasso, Campbell A Patricia
Department of Chemistry, University of Washington, Seattle, WA 98195, USA.
Biopolymers. 2005 Feb 5;77(2):107-20. doi: 10.1002/bip.20190.
MUC1 mucin is a large transmembrane glycoprotein whose extracelluler domain is composed of repeating units of a 20 amino acid sequence. In the cancer associated state, this protein expression becomes upregulated and underglycosylated. Previous studies, which show an enhanced binding of a 5-repeat over a 1-repeat MUC1 peptide to a panel of anti-MUC1 antibodies, have led us to investigate the structural and dynamic consequences of increasing repeat number. Two MUC1 peptides were studied: a 16mer corresponding to slightly less than one full repeat of the MUC1 tandem repeat sequence (GVTSAPDTRPAPGSTA) and a 40mer corresponding to two full repeats of the MUC1 sequence (VTSAPDTRPAPGSTAPPAHG)2. Isotopically labeled versions of these MUC1 peptides were cloned, expressed, purified, and evaluated structurally and dynamically using 15N- and 13C-edited NMR approaches. The data show that MUC1 structure, dynamics, and antibody binding affinity are invariant with increasing repeat number. In light of these results, we conclude that the enhanced antibody affinity of the 5-repeat over the 1-repeat MUC1 peptide is due to multivalency effects, and not due to the development of higher order structure in the longer length peptides. The implications of these results are discussed within the context of a multiple repeat MUC1 breast cancer vaccine design.
粘蛋白1（MUC1）是一种大型跨膜糖蛋白，其细胞外结构域由20个氨基酸序列的重复单元组成。在癌症相关状态下，这种蛋白质的表达上调且糖基化不足。先前的研究表明，与1重复MUC1肽相比，5重复MUC1肽与一组抗MUC1抗体的结合增强，这促使我们研究增加重复数目的结构和动态后果。研究了两种MUC1肽：一种16聚体，对应略少于一个完整重复的MUC1串联重复序列（GVTSAPDTRPAPGSTA），以及一种40聚体，对应两个完整重复的MUC1序列（VTSAPDTRPAPGSTAPPAHG）2。这些MUC1肽的同位素标记版本被克隆、表达、纯化，并使用15N和13C编辑的核磁共振方法进行结构和动态评估。数据表明，MUC1的结构、动力学和抗体结合亲和力不会随着重复数目的增加而变化。鉴于这些结果，我们得出结论，5重复MUC1肽相对于1重复MUC1肽的抗体亲和力增强是由于多价效应，而不是由于较长肽段中高阶结构的形成。在多重复MUC1乳腺癌疫苗设计的背景下讨论了这些结果的意义。
