The cytoplasmic domain of the H-2Ld class I major histocompatibility complex molecule is differentially accessible to immunological and biochemical probes during transport to the cell surface.
An antiserum was generated against a synthetic peptide corresponding to a portion of the cytoplasmic domains of the H-2Ld and H-2Db class I major histocompatibility complex molecules of the mouse. This antibody preparation, R4, binds exclusively to endoglycosidase H-resistant H-2Ld/Db molecules which are not associated with beta 2-microglobulin. Interestingly, acquisition of resistance to endoglycosidase H precedes acquisition of R4 reactivity by 30 min. R4-reactive H-2Ld and H-2Db molecules occur on the cell surface and are phosphorylated in vivo. Other studies show that the tyrosine in the cytoplasmic domain is accessible to radioiodination on only a subset of H-2Ld molecules, and that the two-dimensional electrophoretic profiles of phosphorylated H-2L/Db molecules, of R4-reactive molecules, and of H-2Ld molecules radiolabeled on this cytoplasmic domain tyrosine are virtually identical. R4-reactive H-2Ld molecules do not undergo the peptide- and beta 2-microglobulin-induced conformational changes characteristic of free class I major histocompatibility complex heavy chains. The accessibility of the H-2Ld cytoplasmic domain to R4 and to radioiodination late in biosynthesis and its biological significance are discussed.
Capps
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GG
Department of Biology, Sinsheimer Laboratories, University of California, Santa Cruz 95064.
Zúñiga
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MC
D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport; D002460:Cell Line; D003593:Cytoplasm / Q000378:metabolism; D006183:H-2 Antigens / Q000378:metabolism*; D007457:Iodine Radioisotopes; D007739:L Cells; D051379:Mice; D015335:Molecular Probes; D008969:Molecular Sequence Data; D010766:Phosphorylation; D001613:beta 2-Microglobulin / Q000276:immunology
D006183:H-2 Antigens; D007457:Iodine Radioisotopes; D015335:Molecular Probes; D001613:beta 2-Microglobulin