Hitzel C, Kanzler H, König A, Kummer M P, Brix K, Herzog V, Koch N
Division of Immunobiology, University of Bonn, Germany.
FEBS Lett. 2000 Nov 17;485(1):67-70. doi: 10.1016/s0014-5793(00)02189-x.
The MHCII associated invariant chain isoform Ii41 shows homology to a repeat in thyroglobulin (TgR). We show that the Ii31 isoform, which lacks the TgR-like domain, is sensitive to cathepsin L treatment whereas Ii41 displays substantial resistance. The TgR-like sequence of Ii41 was exchanged for thyroglobulin type-IA and -IB repeats, that contain six or four cysteine residues. Resistance to cathepsin L digestion was maintained upon substitution of the Ii41 TgR for homologous sequences from TgR type-IA. Mutation of a conserved cysteine in the TgR domain of an Ii fusion protein strongly reduced resistance to cathepsin L digestion.
与主要组织相容性复合体II类（MHCII）相关的恒定链异构体Ii41与甲状腺球蛋白中的一个重复序列（TgR）具有同源性。我们发现，缺乏TgR样结构域的Ii31异构体对组织蛋白酶L处理敏感，而Ii41则表现出显著的抗性。将Ii41的TgR样序列替换为含有六个或四个半胱氨酸残基的甲状腺球蛋白IA型和IB型重复序列。用TgR IA型的同源序列替换Ii41的TgR后，对组织蛋白酶L消化的抗性得以维持。Ii融合蛋白的TgR结构域中一个保守半胱氨酸的突变显著降低了对组织蛋白酶L消化的抗性。
