Murakami Y, Yamashita Y, Nakano Y, Ito H O, Yu H, Koga T
Department of Preventive Dentistry, Kyushu University Faculty of Dentistry, Higashi-ku, Fukuoka, Japan.
Infect Immun. 1997 Apr;65(4):1531-5. doi: 10.1128/iai.65.4.1531-1535.1997.
To make clear the role of the C terminus of a surface protein antigen (PAc) of Streptococcus mutans, stepwise truncations beginning at the C terminus of PAc were performed by utilizing site-directed mutagenesis. A remarkable increase in the amount of cell-free PAc was observed upon deletion of four or more amino acid residues at the C terminus. On the other hand, the amount of cell surface PAc gradually decreased when increasing numbers (four or more) of amino acid residues were deleted at the C terminus, and deletion of six amino acids involving both the total charged tail and Leu, an amino acid residue immediately upstream of the charged tail, resulted in a drastic reduction in the amount of cell surface PAc. These results indicate that the cytoplasmic charged tail and Leu residue are required for cell surface localization of PAc in S. mutans.
为明确变形链球菌表面蛋白抗原（PAc）C末端的作用，利用定点诱变技术从PAc的C末端开始进行逐步截短。当在C末端缺失四个或更多氨基酸残基时，观察到无细胞PAc的量显著增加。另一方面，当在C末端缺失的氨基酸残基数增加（四个或更多）时，细胞表面PAc的量逐渐减少，缺失包括总带电荷尾巴和带电荷尾巴上游紧邻的氨基酸残基Leu在内的六个氨基酸，导致细胞表面PAc的量急剧减少。这些结果表明，细胞质带电荷尾巴和Leu残基是PAc在变形链球菌中进行细胞表面定位所必需的。
