Sun J W, Wanda S Y, Camilli A, Curtiss R
Department of Biology, Washington University, St. Louis, Missouri 63130.
J Bacteriol. 1994 Dec;176(23):7213-22. doi: 10.1128/jb.176.23.7213-7222.1994.
Some dextranase-deficient (Dex-) mutants of Streptococcus sobrinus UAB66 (serotype g) synthesize a substance which inhibits dextranase activity (S.-Y. Wanda, A. Camilli, H. M. Murchison, and R. Curtiss III, J. Bacteriol. 176:7206-7212, 1994). This substance produced by the Dex- mutant UAB108 was designated dextranase inhibitor (Dei) and identified as a protein. The Dei gene (dei) from UAB108 has been cloned into pACYC184 to yield pYA2651, which was then used to generate several subclones (pYA2653 to pYA2657). The DNA sequence of dei was determined by using Tn5seq1 transposon mutagenesis of pYA2653. The open reading frame of dei is 990 bp long. It encodes a signal peptide of 38 amino acids and a mature Dei protein of 292 amino acids with a molecular weight of 31,372. The deduced amino acid sequence of Dei shows various degrees of similarity with glucosyltransferases and glucan-binding protein and contains A and C repeating units probably involved in glucan binding. Southern hybridization results showed that the dei probe from UAB108 hybridized to the same-size fragment in S. sobrinus (serotype d and g) DNA, to a different-size fragment in S. downei (serotype h) and S. cricetus (serotype a), and not at all to DNAs from other mutans group of streptococci.
远缘链球菌UAB66（血清型g）的一些葡聚糖酶缺陷型（Dex-）突变体合成了一种抑制葡聚糖酶活性的物质（S.-Y.万达、A.卡米利、H.M.默奇森和R.柯蒂斯三世，《细菌学杂志》176:7206 - 7212，1994年）。由Dex-突变体UAB108产生的这种物质被命名为葡聚糖酶抑制剂（Dei）并鉴定为一种蛋白质。来自UAB108的Dei基因（dei）已被克隆到pACYC184中，产生pYA2651，然后用它来产生几个亚克隆（pYA2653至pYA2657）。通过对pYA2653进行Tn5seq1转座子诱变来确定dei的DNA序列。dei的开放阅读框长990 bp。它编码一个38个氨基酸的信号肽和一个292个氨基酸、分子量为31372的成熟Dei蛋白。Dei推导的氨基酸序列与葡糖基转移酶和葡聚糖结合蛋白有不同程度的相似性，并含有可能参与葡聚糖结合的A和C重复单元。Southern杂交结果表明，来自UAB108的dei探针与远缘链球菌（血清型d和g）DNA中的相同大小片段杂交，与唐氏链球菌（血清型h）和仓鼠链球菌（血清型a）中的不同大小片段杂交，而与其他变形链球菌群的DNA完全不杂交。
