Alcolea J M, Antón L C, Marqués G, Sánchez-Corral P, Vivanco F
Mol Immunol. 1986 Jan;23(1):39-44. doi: 10.1016/0161-5890(86)90169-0.
C1q has 12 binding sites for 1-anilino-8-naphthalene sulphonate (ANS), two per peripheral subunit. This number increases to 18 upon weak-acid-induced conformational transition in the globular heads. One ANS binding site is present in each C gamma 2 domain of human IgG. ANS is bound by C1q with a higher affinity (Ka = 2.07 X 10(6) M-1) than by the Fc fragment (Ka = 9.07 X 10(4) M-1) of human IgGl. Hence the inhibitory capacity of C1q binding to IgG immune complexes of ANS probably reflects its preferential binding to the globular heads of C1q. The characteristics of ANS-C1q binding may in part explain the hydrophobic component of the C1q-IgG interaction. It is suggested that an ionic-hydrophobic two-step process is involved in the contact between C1q and IgG.
C1q有12个与1-苯胺基-8-萘磺酸盐（ANS）结合的位点，每个外周亚基有两个。在球蛋白头部发生弱酸诱导的构象转变后，这个数字增加到18。人IgG的每个Cγ2结构域中有一个ANS结合位点。与人类IgG1的Fc片段（Ka = 9.07×10⁴ M⁻¹）相比，C1q与ANS的结合亲和力更高（Ka = 2.07×10⁶ M⁻¹）。因此，ANS对C1q结合至IgG免疫复合物的抑制能力可能反映了其与C1q球蛋白头部的优先结合。ANS-C1q结合的特性可能部分解释了C1q-IgG相互作用的疏水成分。有人提出，C1q与IgG之间的接触涉及离子-疏水两步过程。
