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Immunological significances of invariant chain from the aspect of its structural homology with the cystatin family
Author(s) -
Katunuma Nobuhiko,
Kakegawa Hisao,
Matsunaga Youichi,
Saibara Toshiji
Publication year - 1994
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(94)00657-1
Subject(s) - cathepsin , cd74 , chemistry , cathepsin o , biochemistry , cathepsin c , cathepsin l , cysteine protease , immunoglobulin light chain , cysteine , cathepsin l1 , microbiology and biotechnology , mhc class ii , homology (biology) , cathepsin a , cathepsin b , cathepsin h , dimer , biology , major histocompatibility complex , enzyme , amino acid , gene , immunology , antibody , organic chemistry
The primary structure of p31 of invariant chain (Ii‐chain) shows about 50% homology with those of the cystatin family which are endogenous cysteine protease inhibitors. The binding domains between Ii‐chain and HLA‐DR‐7 were estimated from the structural homology between cystatin and Ii‐chain and also between cathepsins and DR‐7, respectively. The QL 64–71 and GS 76–88 of Ii‐Chain were estimated to be the binding domains with GG 45–51 , and VS 57–63 of HLA‐DR7, respectively. The purified human Ii‐chain from spleen is capable of forming four molecular forms from monomer to tetramer by redox‐potential dependent disulfide bond formation. The Ii‐chain inhibits cathepsin L and H competitively as a dimer and the K i value for cathepsin L was 4.1 × 10 −8 M, but cathepsin B was not inhibited at all. The Ii‐chain showed mainly a dimer (60 kDa) under the assay condition of cathepsins with cysteine and was not degraded by these cathepsins. The Ii‐chain may play an important role in the regulation of antigenic peptide presentation to MHC class II.