Satyanarayana J, Situ H, Narasimhamurthy S, Bhayani N, Bobek L A, Levine M J
Department of Oral Biology, State University of New York at Buffalo, 14214-3092, USA.
J Pept Res. 2000 Nov;56(5):275-82. doi: 10.1034/j.1399-3011.2000.00765.x.
Domain 1 of the low-molecular-weight human salivary mucin, designated MUC7 D1, spans the 51 N-terminal amino acid residues. This domain contains a 15-residue basic histidine-rich subdomain (R3-Q17) which has 53% sequence similarity to histatin 5 (Hsn-5), a salivary molecule known to exert potent in vitro cidal activity against Candida albicans and many other medically important fungi. The MUC7 D1-15mer and its derivatives have previously been synthesized in our laboratory and their candidacidal activities have been found to be inferior to that of Hsn-5. We were therefore intrigued to explore the candidacidal potency of the full-length MUC7 D1 (51-mer). Linear solid-phase synthesis of this domain has been accomplished following standard Fmoc chemistry. The problems of partial coupling, owing to the peptide chain length, at several stages of the solid-phase step-by-step synthesis were circumvented either by double-coupling techniques or efficient coupling procedures. The MUC7 D1 peptide was purified to homogeneity by conventional reverse-phase HPLC using two columns connected in series. Secondary structure of the purified peptide was assessed by circular dichroism (CD) spectroscopy in phosphate buffer and trifluoroethanol and compared to that of MUC7 D1-15mer and Hsn-5. The MUC7 D1 candidacidal activity was assessed against azole-sensitive and azole-resistant C. albicans strains and was found, unlike that of the MUC7 D1-15mer, to be comparable with that of Hsn-5, indicating that in addition to Hsn-5, MUC7 D1 could provide an attractive alternative to the classical antifungal agents. The candidacidal potency of MUC7 D1, like that of MUC7 D1-15mer, and of Hsn-5, appears to be largely dependent on peptide charge, irrespective of alpha-helical structure.
低分子量人唾液粘蛋白的结构域1，命名为MUC7 D1，跨越51个N端氨基酸残基。该结构域包含一个由15个残基组成的富含组氨酸的碱性亚结构域（R3-Q17），其与组蛋白5（Hsn-5）具有53%的序列相似性，Hsn-5是一种唾液分子，已知在体外对白色念珠菌和许多其他医学上重要的真菌具有强大的杀菌活性。MUC7 D1-15聚体及其衍生物此前已在我们实验室合成，其杀念珠菌活性被发现低于Hsn-5。因此，我们很感兴趣地探索全长MUC7 D1（51聚体）的杀念珠菌效力。按照标准的Fmoc化学方法完成了该结构域的线性固相合成。在固相逐步合成的几个阶段，由于肽链长度导致的部分偶联问题，通过双偶联技术或高效偶联程序得以解决。使用串联的两根柱子，通过常规反相高效液相色谱法将MUC7 D1肽纯化至同质。在磷酸盐缓冲液和三氟乙醇中，通过圆二色性（CD）光谱评估纯化肽的二级结构，并与MUC7 D1-15聚体和Hsn-5的二级结构进行比较。针对唑类敏感和唑类耐药的白色念珠菌菌株评估了MUC7 D1的杀念珠菌活性，结果发现，与MUC7 D1-15聚体不同，其杀念珠菌活性与Hsn-5相当，这表明除了Hsn-5之外，MUC7 D1可以为传统抗真菌药物提供一个有吸引力的替代选择。MUC7 D1的杀念珠菌效力，与MUC7 D1-15聚体以及Hsn-5一样，似乎在很大程度上取决于肽电荷，而与α-螺旋结构无关。
