Open AccessPartial cDNA sequence encoding a nuclear pore protein modified by O-linked N-acetylglucosamine.
Author(s) -
Mara D’Onofrio,
Christopher M. Starr,
Min K. Park,
Gordon D. Holt,
Robert S. Haltiwanger,
Gerald W. Hart,
John A. Hanover
Publication year - 1988
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.85.24.9595
Subject(s) - complementary dna , peptide sequence , open reading frame , biochemistry , biology , microbiology and biotechnology , protein primary structure , glycoprotein , glycosylation , gel electrophoresis , cdna library , molecular mass , gene , enzyme
The nuclear pore complex contains a family of proteins ranging in molecular mass from 35 to 220 kDa that are glycosylated with O-linked N-acetylglucosamine (GlcNAc) residues. We sought to determine the primary sequence of a nuclear pore protein modified by O-linked GlcNAc. The major (62 kDa) nuclear pore glycoprotein (np62) was purified from rat liver nuclear envelopes by immunoaffinity chromatography and preparative gel electrophoresis. After CNBr fragmentation, a glycopeptide was isolated and microsequenced. An oligonucleotide probe based on this sequence information was used to screen a lambda gt11 cDNA library constructed from poly(A) mRNA of the rat thyroid cell line FRTL-5. A clone (B5) was isolated and shown to hybridize to a single 2.5-kilobase species in poly(A) mRNA from rat liver and FRTL-5. This insert was sequenced and found to contain a 691-base-pair cDNA encoding a 155-amino acid open reading frame. This open reading frame contained a CNBr fragment identical to the original glycopeptide sequence and a second CNBr fragment corresponding to a nonglycosylated peptide that was also isolated from the purified pore glycoprotein. The B5 cDNA produced a beta-galactosidase fusion protein of the size predicted by the open reading frame. Analysis of the residues making up a presumptive glycosylation site suggests that the sequence is unlike any known sites for enzymatic N- or O-linked glycosylation. The partial sequence of the 62-kDa nuclear pore glycoprotein shows little similarity to other characterized proteins and elucidates structural features of a member of the family of nuclear pore glycoproteins.