Isolation and structural characterization of a cDNA clone encoding rat gastric intrinsic factor.

B. K. Dieckgraefe, B. Seetharam, L. Banaszak, J. F. Leykam, D. H. Alpers

Research output: Contribution to journalArticlepeer-review

29 Scopus citations


Rat intrinsic factor (IF) has been purified and proteolytic fragments were sequenced. A cDNA library was constructed from size-enriched gastric poly(A)+ RNA and screened for IF-positive clones by antibody and synthetic oligodeoxynucleotide probe hybridization. An IF clone was isolated and sequenced, revealing a predicted primary amino acid sequence in the coding region of 421 amino acids and a putative signal sequence of 22 amino acids. The primary translation product of IF produced in a cell-free translation system displayed cobalamin (Cbl)-binding activity without proteolytic processing or glycosylation. The amino-terminal region of IF showed significant secondary structural and hydropathic homologies with the nucleotide-binding domain in NAD-dependent oxidoreductases. Alignment of the first 80 residues of IF, following the signal peptide, demonstrated homology with the nucleotide-binding domain of cytoplasmic malate dehydrogenase. Based on these data, we propose a model of IF tertiary structure in which the Cbl-binding domain resides in the NH2-terminal half of the protein.

Original languageEnglish
Pages (from-to)46-50
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number1
StatePublished - Jan 1988

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