Identification of p70 and p80 associations with class II MHC molecules and Ii.
Two proteins, p70 and p80, were found in chemically crosslinked complexes with class II MHC molecules and Ii after 3-12 hr labelings with [35S]methionine. Two-dimensional, nonreduced/reduced SDS gel electrophoresis of immunoprecipitated complexes revealed 1) endogenous disulfide linkages between Ii-Ii and Ii-p70 and 2) chemically crosslinked, nearest neighbors of alpha-beta, alpha-Ii, Ii-p70, and alpha-p80. Although such nearest neighbors within multimeric complexes were identified as dimers in nonreduced/reduced 2D gels, stoichiometries could not be determined in the high molecular weight complex(es), which included alpha, beta, Ii, p70, and p80, and were not separated in the first dimension. p80 was not the chondroitin-sulfate form of Ii (Ii-CS) because it was not electrophoretically heterogeneous and was not sensitive to chondroitinase ABC. p70 was not hsp72/74 detected with C92 or N27 mAbs, and p80 was not BiP detected with its respective mAb. While only these two proteins associated prominently with class II MHC antigens and Ii late after synthesis, their functions are unknown.
Sorli
C H
CH
Department of Pharmacology, University of Massachusetts Medical Center, Worcester 01655.
Reisert
P S
PS
Welch
W J
WJ
Humphreys
R E
RE
D000911:Antibodies, Monoclonal; D000944:Antigens, Differentiation, B-Lymphocyte; D000951:Antigens, Neoplasm / Q000302:isolation & purification; D002460:Cell Line; D015180:Electrophoresis, Gel, Two-Dimensional; D006360:Heat-Shock Proteins / Q000302:isolation & purification; D000949:Histocompatibility Antigens Class II / Q000235:genetics / Q000302:isolation & purification*; D006801:Humans; D007700:Kinetics; D008715:Methionine / Q000378:metabolism; D008970:Molecular Weight; D011485:Protein Binding; D014176:Protein Biosynthesis; D011506:Proteins / Q000302:isolation & purification*
D000911:Antibodies, Monoclonal; D000944:Antigens, Differentiation, B-Lymphocyte; D000951:Antigens, Neoplasm; D006360:Heat-Shock Proteins; D000949:Histocompatibility Antigens Class II; D011506:Proteins; C045084:invariant chain; D008715:Methionine