Jacobs A A, van Mechelen J R, de Graaf F K
Biochim Biophys Acta. 1985 Nov 29;832(2):148-55. doi: 10.1016/0167-4838(85)90326-7.
The role of specific amino acid residues of the K88ab and K99 fibrillar adhesins in the binding to erythrocytes and antibodies has been studied by chemical modification. It appeared that: (1) The integrity of the single disulfide bridge in the K99 subunits is essential for the binding of the fibrillae to the glycolipid receptors, but not for the recognition and binding of specific anti-K99 antibodies. (2) Modification of one lysine residue per subunit with 4-chloro-3,5-dinitrobenzoate results in the loss of the adhesive capacity of K99 fibrillae. Lysine residue are not important for the adhesive activity of K88ab fibrillae. Three or five lysine residues per subunit, respectively, can be modified without an effect on the immunological properties of the K99 and K88ab fibrillae. (3) Limited reaction of K99 and K88ab fibrillae with 2,3-butanedione destroys the adhesive activity of both fibrillae. This inactivation corresponds with the loss of one (K99) or two (K88ab) arginine residues per subunit. Ultimately, in K99 three, and in K88ab four, arginine residues per subunit can be modified without affecting the binding of specific antibodies. (4) Modification of five out of the nine carboxyl groups contained in the K99 subunit suppresses the recognition of specific anti-K99 antibodies, but carboxylates are not important for the adhesive activity of K99 fibrillae. Modification of two additional carboxylates in K99 results in an insoluble product. (5) Tyrosine residues are most probably not present in the adhesive or antigenic sites of K99 fibrillae. Modification of six out of the ten tyrosine residues in the K88ab subunit results in a decrease in adhesive activity but has no effect on the reaction with anti-K88ab antibodies.
通过化学修饰研究了K88ab和K99纤丝状黏附素的特定氨基酸残基在与红细胞及抗体结合中的作用。结果表明：(1) K99亚基中单个二硫键的完整性对于纤丝与糖脂受体的结合至关重要，但对于特异性抗K99抗体的识别和结合并非必需。(2) 用4-氯-3,5-二硝基苯甲酸修饰每个亚基的一个赖氨酸残基会导致K99纤丝黏附能力丧失。赖氨酸残基对K88ab纤丝的黏附活性并不重要。每个亚基分别修饰三个或五个赖氨酸残基对K99和K88ab纤丝的免疫学特性没有影响。(3) K99和K88ab纤丝与2,3-丁二酮的有限反应会破坏两种纤丝的黏附活性。这种失活与每个亚基一个（K99）或两个（K88ab）精氨酸残基的丧失相对应。最终，每个亚基修饰三个（K99）和四个（K88ab）精氨酸残基不影响特异性抗体的结合。(4) K99亚基中九个羧基中的五个被修饰会抑制特异性抗K99抗体的识别，但羧酸盐对K99纤丝的黏附活性并不重要。在K99中再修饰两个羧酸盐会产生不溶性产物。(5) 酪氨酸残基很可能不存在于K99纤丝的黏附或抗原位点。K88ab亚基中十个酪氨酸残基中的六个被修饰会导致黏附活性降低，但对与抗K88ab抗体的反应没有影响。
