A proteasome-related gene between the two ABC transporter loci in the class II region of the human MHC

• Published in: Nature (London) Vol. 353; no. 6342; pp. 357 - 360
• Main Authors: Glynne, Richard, Powis, Stephen H, Beck, Stephan, Kelly, Adrian, Kerr, Lesley-Anne, Trowsdale, John
• Format: Journal Article
• Language: English
• Published: London Nature Publishing 26.09.1991; Nature Publishing Group
• Subjects: ABC transporter; Amino Acid Sequence; Base Sequence; Biochemistry; Biological and medical sciences; Biological Transport - genetics; Chromosome Mapping; Cysteine Endopeptidases - genetics; Fundamental and applied biological sciences. Psychology; genes; Genes. Genome; Genetics; HLA-D Antigens - genetics; Humans; Immune system; Major Histocompatibility Complex - genetics; Molecular and cellular biology; Molecular genetics; Molecular Sequence Data; Molecular Weight; Multienzyme Complexes - genetics; Peptides; Peptides - genetics; Proteasome Endopeptidase Complex; Protein Processing, Post-Translational - genetics; Sequence Homology, Nucleic Acid; Human; Cartography; Molecular processing; Multienzyme complex; Enzyme; Gene product; Proteinase; Major histocompatibility system; Class II histocompatibility antigen; Gene organization; Antigen; Immunogenetics; Gene; Membrane transport; Locus
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/353357a0

It is now possible to paint a detailed picture of how cytoplasmic proteins are handled by the immune system. They are apparently degraded in the cytoplasm into peptides. These are then transported into the endoplasmic reticulum where they encounter class I major histocompatibility complex (MHC) molecules. Once loaded with peptide, the HLA molecules move through the Golgi apparatus to the cell membrane. Until recently, it had not been established how peptides without signal sequences cross the ER membrane. However, a number of papers have now described a pair of membrane transporter genes of the ABC (ATP-binding cassette) super-family which are attractive candidates for this function. Both transporter genes, which may encode two halves of a heterodimer, are situated in the class II region of the MHC. There is evidence that other putative components of the processing machinery, the LMPs (low molecular mass polypeptides), are also encoded in the MHC. Similarities between the properties of the LMPs and a large intracellular protease complex, called proteasome, have led to the suggestion that LMPs are involved in processing antigens. We have now identified a human gene with sequence homology to proteasome components. Remarkably, this gene maps between the two putative peptide transporter genes.