The complete sequence of the mRNA for the HLA-DR-associated invariant chain reveals a polypeptide with an unusual transmembrane polarity.
A non-polymorphic polypeptide is associated intracellularly with the alpha and beta chains of murine Ia antigens and of human HLA-DR antigens. The exact role and the structure of this invariant chain have not been determined so far. A cDNA clone encoding the 33 000 dalton human invariant chain has been isolated. The nucleotide sequence of a near full-length cDNA clone, together with the sequence of the 5' portion of the mRNA determined by primer-extension, are reported here. The protein structure deduced from that sequence shows an unusual feature: the presence of a hydrophobic transmembrane region near the NH2 terminus, and of two glycosylation sites near the middle, indicates that the invariant chain has a polarity of membrane insertion which is inverted relative to histocompatibility antigens and most transmembrane proteins.
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002462:Cell Membrane / Q000276:immunology; D004247:DNA; D004274:DNA, Recombinant; D006684:HLA-DR Antigens; D000949:Histocompatibility Antigens Class II; D006801:Humans; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000235:genetics / Q000276:immunology; D051379:Mice; D012333:RNA, Messenger
D004274:DNA, Recombinant; D006684:HLA-DR Antigens; D000949:Histocompatibility Antigens Class II; D046911:Macromolecular Substances; D008565:Membrane Proteins; D012333:RNA, Messenger; D004247:DNA