title: MP38 contains the membrane-embedded domain of the lens fiber gap junction protein MP70.
abstract: A 70-kDa lens membrane polypeptide (MP70) is a specific component of the fiber gap junctions. The C-terminal portion of MP70 is removed by age-related proteolytic processing, leaving an N-terminal 38-kDa polypeptide (MP38) in the membrane. Membrane association and topology of MP70 and of its processed form MP38 have been studied by hydrophobic labeling with 3-(trifluoromethyl)-3-(m-[125I]iodophenyl)diazirine and phenyl isothio[14C]cyanate. Membrane-embedded segments have been identified. They are localized in the N-terminal 30-kDa portion of MP70 and MP38. The C-terminal 40-kDa portion of MP70 appears to be exposed entirely at the cytoplasmic side of the junctional membranes. Hence, potentially poreforming peptide segments in the MP70 molecule are conserved upon age-related processing to MP38.
authors.affiliation: Department of Cellular & Molecular Biology, University of Auckland, New Zealand.
authors.forename: J
authors.initials: J
authors.lastname: Kistler
authors.forename: J
authors.initials: J
authors.lastname: Schaller
authors.forename: H
authors.initials: H
authors.lastname: Sigrist
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001389:Azirines / Q000378:metabolism; D001665:Binding Sites; D002462:Cell Membrane / Q000378:metabolism; D017630:Connexins; D017879:Isothiocyanates; D007700:Kinetics; D007908:Lens, Crystalline / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011485:Protein Binding; D011487:Protein Conformation; D012689:Sequence Homology, Nucleic Acid; D012756:Sheep; D013861:Thiocyanates / Q000378:metabolism
chemical_list: D001389:Azirines; D017630:Connexins; D017879:Isothiocyanates; D008565:Membrane Proteins; D013861:Thiocyanates; C005441:phenylisothiocyanate; C033174:3-(trifluoromethyl)-3-(3-iodophenyl)diazirine